import java.io.*;
import java.util.*;
import java.math.*;

//Mann Shah [ DAIICT ].

public class Main {
	static long mod = (long) (1e9+7);
	static InputReader in;
    static PrintWriter out;
    static Debugger deb;  
    
    	public static void main(String args[] ) throws NumberFormatException, IOException  {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    int[] f= new int[6];
	    int[] a  =in.nextIntArray(5);
	    for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    }
	    int ans=0;
	    for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    }
	    out.println(ans);
	    
	    out.close();
	}




/* TC space


 */	
		static class InputReader
	    {
	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

	        public InputReader(InputStream stream){
	                this.stream = stream;
	        }
	        public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        }

	        public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        }

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }
	        
	        public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        }

	        public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        }

	        public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        }

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

	        public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        }

	    }
		
		static class Debugger{
			public void n(int x) {
				out.println(x);
			}
			
			public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			}
		}
	
		
}


class Pair { 
   int x; 
   int y; 
   // Constructor 
   public Pair(int x, int y) 
   { 
       this.x = x; 
       this.y = y; 
   } 
	@Override
	public boolean equals(Object o) {
	    if (this == o) return true;
	    if (!(o instanceof Pair)) return false;
	    Pair p = (Pair) o;
	    return x == p.x && y == p.y;
	}	
	@Override
	public int hashCode() {
		return (""+x+"-"+y).hashCode();
	}	
}  import java.io.*; io.* java import java.util.*; util.* java import java.math.*; math.* java public class Main {
	static long mod = (long) (1e9+7);
	static InputReader in;
    static PrintWriter out;
    static Debugger deb;  
    
    	public static void main(String args[] ) throws NumberFormatException, IOException  {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    int[] f= new int[6];
	    int[] a  =in.nextIntArray(5);
	    for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    }
	    int ans=0;
	    for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    }
	    out.println(ans);
	    
	    out.close();
	}




/* TC space


 */	
		static class InputReader
	    {
	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

	        public InputReader(InputStream stream){
	                this.stream = stream;
	        }
	        public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        }

	        public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        }

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }
	        
	        public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        }

	        public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        }

	        public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        }

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

	        public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        }

	    }
		
		static class Debugger{
			public void n(int x) {
				out.println(x);
			}
			
			public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			}
		}
	
		
} Main static long mod = (long) (1e9+7); mod (long) (1e9+7) 1e9 7 static InputReader in; in static PrintWriter out; out static Debugger deb; deb public static void main(String args[] ) throws NumberFormatException, IOException  {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    int[] f= new int[6];
	    int[] a  =in.nextIntArray(5);
	    for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    }
	    int ans=0;
	    for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    }
	    out.println(ans);
	    
	    out.close();
	} main {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    int[] f= new int[6];
	    int[] a  =in.nextIntArray(5);
	    for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    }
	    int ans=0;
	    for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    }
	    out.println(ans);
	    
	    out.close();
	} in = new InputReader(System.in) in new InputReader(System.in) out = new PrintWriter(System.out) out new PrintWriter(System.out) deb = new Debugger() deb new Debugger() int[] f= new int[6]; f new int[6] 6 int[] a  =in.nextIntArray(5); a in.nextIntArray(5) in.nextIntArray in 5 for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    } int i=0; int i=0; i 0 i<5 i 5 i++ i++ i {
	    		f[a[i]]++;
	    } {
	    		f[a[i]]++;
	    } f[a[i]]++ f[a[i]] f a[i] a i int ans=0; ans 0 for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    } int i=1; int i=1; i 1 i<=5 i 5 i++ i++ i {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    } {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    } if(f[i]==0) {
	    			ans  = i;
	    		} f[i]==0 f[i] f i 0 {
	    			ans  = i;
	    		} ans  = i ans i out.println(ans) out.println out ans out.close() out.close out String args[] args 		static class InputReader
	    {
	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

	        public InputReader(InputStream stream){
	                this.stream = stream;
	        }
	        public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        }

	        public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        }

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }
	        
	        public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        }

	        public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        }

	        public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        }

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

	        public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        }

	    } InputReader private final InputStream stream; stream private final byte[] buf = new byte[8192]; buf new byte[8192] 8192 private int curChar curChar snumChars; snumChars private SpaceCharFilter filter; filter public InputReader(InputStream stream){
	                this.stream = stream;
	        } InputReader {
	                this.stream = stream;
	        } this.stream = stream this.stream this this.stream stream InputStream stream stream public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        } snext {
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        } if (snumChars == -1) throw new InputMismatchException(); snumChars == -1 snumChars -1 1 throw new InputMismatchException(); new InputMismatchException() if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                } curChar >= snumChars curChar snumChars {
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                } curChar = 0 curChar 0 try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        } catch (IOException e){
                                throw new InputMismatchException();
                        } IOException e {
                                throw new InputMismatchException();
                        } throw new InputMismatchException(); new InputMismatchException() {
                                snumChars = stream.read(buf);
                        } snumChars = stream.read(buf) snumChars stream.read(buf) stream.read stream buf if (snumChars <= 0)
                                return -1; snumChars <= 0 snumChars 0 return -1; -1 1 return buf[curChar++]; buf[curChar++] buf curChar++ curChar public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        } nextInt {
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        } int c = snext(); c snext() snext while (isSpaceChar(c)){
	                    c = snext();
	                } isSpaceChar(c) isSpaceChar c {
	                    c = snext();
	                } c = snext() c snext() snext int sgn = 1; sgn 1 if (c == '-'){
                        sgn = -1;
                        c = snext();
	                } c == '-' c '-' {
                        sgn = -1;
                        c = snext();
	                } sgn = -1 sgn -1 1 c = snext() c snext() snext int res = 0; res 0 do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } if (c < '0' || c > '9')
                                throw new InputMismatchException(); c < '0' || c > '9' c < '0' c '0' c > '9' c '9' throw new InputMismatchException(); new InputMismatchException() res *= 10 res 10 res += c - '0' res c - '0' c '0' c = snext() c snext() snext return res * sgn; res * sgn res sgn public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        } nextLong {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        } int c = snext(); c snext() snext while (isSpaceChar(c))
	                {
	                        c = snext();
	                } isSpaceChar(c) isSpaceChar c {
	                        c = snext();
	                } c = snext() c snext() snext int sgn = 1; sgn 1 if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                } c == '-' c '-' {
	                        sgn = -1;
	                        c = snext();
	                } sgn = -1 sgn -1 1 c = snext() c snext() snext long res = 0; res 0 do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } if (c < '0' || c > '9')
	                                throw new InputMismatchException(); c < '0' || c > '9' c < '0' c '0' c > '9' c '9' throw new InputMismatchException(); new InputMismatchException() res *= 10 res 10 res += c - '0' res c - '0' c '0' c = snext() c snext() snext return res * sgn; res * sgn res sgn public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        } nextIntArray {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        } int a[] = new int[n]; a new int[n] n for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
	                        a[i] = nextInt();
	                } {
	                        a[i] = nextInt();
	                } a[i] = nextInt() a[i] a i nextInt() nextInt return a; a int n n public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        } nextLongArray {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        } long a[] = new long[n]; a new long[n] n for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
	                        a[i] = nextLong();
	                } {
	                        a[i] = nextLong();
	                } a[i] = nextLong() a[i] a i nextLong() nextLong return a; a int n n public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        } nextArrayList {
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        } ArrayList<Integer> x = new ArrayList<Integer>(); x new ArrayList<Integer>() for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
	        				int v = in.nextInt();
	        				x.add(v);
	        			} {
	        				int v = in.nextInt();
	        				x.add(v);
	        			} int v = in.nextInt(); v in.nextInt() in.nextInt in x.add(v) x.add x v return x; x int n n public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        } readString {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        } int c = snext(); c snext() snext while (isSpaceChar(c))
	                {
	                        c = snext();
	                } isSpaceChar(c) isSpaceChar c {
	                        c = snext();
	                } c = snext() c snext() snext StringBuilder res = new StringBuilder(); res new StringBuilder() do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } res.appendCodePoint(c) res.appendCodePoint res c c = snext() c snext() snext return res.toString(); res.toString() res.toString res public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        } nextLine {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        } int c = snext(); c snext() snext while (isSpaceChar(c))
	                        c = snext(); isSpaceChar(c) isSpaceChar c c = snext() c snext() snext StringBuilder res = new StringBuilder(); res new StringBuilder() do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c)); !isEndOfLine(c) isEndOfLine(c) isEndOfLine c {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } res.appendCodePoint(c) res.appendCodePoint res c c = snext() c snext() snext return res.toString(); res.toString() res.toString res public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        } isSpaceChar {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        } if (filter != null)
	                        return filter.isSpaceChar(c); filter != null filter null return filter.isSpaceChar(c); filter.isSpaceChar(c) filter.isSpaceChar filter c return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == '\t' c == '\r' c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == ' ' c ' ' c == '\n' c '\n' c == '\r' c '\r' c == '\t' c '\t' c == -1 c -1 1 int c c private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        } isEndOfLine {
	                return c == '\n' || c == '\r' || c == -1;
	        } return c == '\n' || c == '\r' || c == -1; c == '\n' || c == '\r' || c == -1 c == '\n' || c == '\r' || c == -1 c == '\n' c '\n' c == '\r' c '\r' c == -1 c -1 1 int c c public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        } SpaceCharFilter public boolean isSpaceChar(int ch); isSpaceChar int ch ch static class Debugger{
			public void n(int x) {
				out.println(x);
			}
			
			public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			}
		} Debugger public void n(int x) {
				out.println(x);
			} n {
				out.println(x);
			} out.println(x) out.println out x int x x public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			} a {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			} StringBuilder sb = new StringBuilder(); sb new StringBuilder() for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        } int i=0; int i=0; i 0 i<a.length i a.length a a.length i++ i++ i {
		        		sb.append(a[i]+" ");
		        } {
		        		sb.append(a[i]+" ");
		        } sb.append(a[i]+" ") sb.append sb a[i]+" " a[i] a i " " out.println(sb.toString()) out.println out sb.toString() sb.toString sb int[] a a class Pair { 
   int x; 
   int y; 
   // Constructor 
   public Pair(int x, int y) 
   { 
       this.x = x; 
       this.y = y; 
   } 
	@Override
	public boolean equals(Object o) {
	    if (this == o) return true;
	    if (!(o instanceof Pair)) return false;
	    Pair p = (Pair) o;
	    return x == p.x && y == p.y;
	}	
	@Override
	public int hashCode() {
		return (""+x+"-"+y).hashCode();
	}	
} Pair int x; x int y; y // Constructor 
   public Pair(int x, int y) 
   { 
       this.x = x; 
       this.y = y; 
   } Pair { 
       this.x = x; 
       this.y = y; 
   } this.x = x this.x this this.x x this.y = y this.y this this.y y int x x int y y @Override
	public boolean equals(Object o) {
	    if (this == o) return true;
	    if (!(o instanceof Pair)) return false;
	    Pair p = (Pair) o;
	    return x == p.x && y == p.y;
	} equals {
	    if (this == o) return true;
	    if (!(o instanceof Pair)) return false;
	    Pair p = (Pair) o;
	    return x == p.x && y == p.y;
	} if (this == o) return true; this == o this o return true; true if (!(o instanceof Pair)) return false; !(o instanceof Pair) (o instanceof Pair) o Pair return false; false Pair p = (Pair) o; p (Pair) o return x == p.x && y == p.y; x == p.x && y == p.y x == p.x x p.x p p.x y == p.y y p.y p p.y Object o o @Override
	public int hashCode() {
		return (""+x+"-"+y).hashCode();
	} hashCode {
		return (""+x+"-"+y).hashCode();
	} return (""+x+"-"+y).hashCode(); (""+x+"-"+y).hashCode() (""+x+"-"+y).hashCode (""+x+"-"+y) "-" ""+x+"-"+y "" x "-" y public class Main {
	static long mod = (long) (1e9+7);
	static InputReader in;
    static PrintWriter out;
    static Debugger deb;  
    
    	public static void main(String args[] ) throws NumberFormatException, IOException  {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    int[] f= new int[6];
	    int[] a  =in.nextIntArray(5);
	    for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    }
	    int ans=0;
	    for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    }
	    out.println(ans);
	    
	    out.close();
	}




/* TC space


 */	
		static class InputReader
	    {
	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

	        public InputReader(InputStream stream){
	                this.stream = stream;
	        }
	        public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        }

	        public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        }

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }
	        
	        public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        }

	        public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        }

	        public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        }

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

	        public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        }

	    }
		
		static class Debugger{
			public void n(int x) {
				out.println(x);
			}
			
			public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			}
		}
	
		
} public class Main {
	static long mod = (long) (1e9+7);
	static InputReader in;
    static PrintWriter out;
    static Debugger deb;  
    
    	public static void main(String args[] ) throws NumberFormatException, IOException  {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    int[] f= new int[6];
	    int[] a  =in.nextIntArray(5);
	    for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    }
	    int ans=0;
	    for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    }
	    out.println(ans);
	    
	    out.close();
	}




/* TC space


 */	
		static class InputReader
	    {
	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

	        public InputReader(InputStream stream){
	                this.stream = stream;
	        }
	        public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        }

	        public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        }

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }
	        
	        public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        }

	        public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        }

	        public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        }

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

	        public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        }

	    }
		
		static class Debugger{
			public void n(int x) {
				out.println(x);
			}
			
			public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			}
		}
	
		
} Main
import java.io.*;
import java.util.*;
import java.math.*;

//Mann Shah [ DAIICT ].

public class Main {
	static long mod = (long) (1e9+7);
	static InputReader in;
    static PrintWriter out;
    static Debugger deb;  
    
    	public static void main(String args[] ) throws NumberFormatException, IOException  {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    int[] f= new int[6];
	    int[] a  =in.nextIntArray(5);
	    for(int i=0;i<5;i++) {
	    		f[a[i]]++;
	    }
	    int ans=0;
	    for(int i=1;i<=5;i++) {
	    		if(f[i]==0) {
	    			ans  = i;
	    		}
	    }
	    out.println(ans);
	    
	    out.close();
	}




/* TC space


 */	
		static class InputReader
	    {
	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

	        public InputReader(InputStream stream){
	                this.stream = stream;
	        }
	        public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        }

	        public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        }

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }
	        
	        public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        }

	        public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        }

	        public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        }

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

	        public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        }

	    }
		
		static class Debugger{
			public void n(int x) {
				out.println(x);
			}
			
			public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			}
		}
	
		
}


class Pair { 
   int x; 
   int y; 
   // Constructor 
   public Pair(int x, int y) 
   { 
       this.x = x; 
       this.y = y; 
   } 
	@Override
	public boolean equals(Object o) {
	    if (this == o) return true;
	    if (!(o instanceof Pair)) return false;
	    Pair p = (Pair) o;
	    return x == p.x && y == p.y;
	}	
	@Override
	public int hashCode() {
		return (""+x+"-"+y).hashCode();
	}	
} 
