import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Main {
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());

        String[] S_Array = st.nextToken().split("");
        st = new StringTokenizer(br.readLine());
        String[] T_Array = st.nextToken().split("");

        int result = 0;

        for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        }
        
        pw.println(result);
        br.close();
        pw.close();
    }
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.PrintWriter; PrintWriter java.io import java.util.StringTokenizer; StringTokenizer java.util public class Main {
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());

        String[] S_Array = st.nextToken().split("");
        st = new StringTokenizer(br.readLine());
        String[] T_Array = st.nextToken().split("");

        int result = 0;

        for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        }
        
        pw.println(result);
        br.close();
        pw.close();
    }
} Main public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());

        String[] S_Array = st.nextToken().split("");
        st = new StringTokenizer(br.readLine());
        String[] T_Array = st.nextToken().split("");

        int result = 0;

        for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        }
        
        pw.println(result);
        br.close();
        pw.close();
    } main {
        BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());

        String[] S_Array = st.nextToken().split("");
        st = new StringTokenizer(br.readLine());
        String[] T_Array = st.nextToken().split("");

        int result = 0;

        for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        }
        
        pw.println(result);
        br.close();
        pw.close();
    } BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in)); br new BufferedReader(new java.io.InputStreamReader(System.in)) PrintWriter pw = new PrintWriter(System.out); pw new PrintWriter(System.out) StringTokenizer st = new StringTokenizer(br.readLine()); st new StringTokenizer(br.readLine()) String[] S_Array = st.nextToken().split(""); S_Array st.nextToken().split("") st.nextToken().split st.nextToken() st.nextToken st "" st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) String[] T_Array = st.nextToken().split(""); T_Array st.nextToken().split("") st.nextToken().split st.nextToken() st.nextToken st "" int result = 0; result 0 for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        } int i = 0; int i = 0; i 0 i < S_Array.length i S_Array.length S_Array S_Array.length i++ i++ i {
            if(!S_Array[i].equals(T_Array[i])) result++;
        } {
            if(!S_Array[i].equals(T_Array[i])) result++;
        } if(!S_Array[i].equals(T_Array[i])) result++; !S_Array[i].equals(T_Array[i]) S_Array[i].equals(T_Array[i]) S_Array[i].equals S_Array[i] S_Array i T_Array[i] T_Array i result++ result pw.println(result) pw.println pw result br.close() br.close br pw.close() pw.close pw String[] args args public class Main {
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());

        String[] S_Array = st.nextToken().split("");
        st = new StringTokenizer(br.readLine());
        String[] T_Array = st.nextToken().split("");

        int result = 0;

        for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        }
        
        pw.println(result);
        br.close();
        pw.close();
    }
} public class Main {
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());

        String[] S_Array = st.nextToken().split("");
        st = new StringTokenizer(br.readLine());
        String[] T_Array = st.nextToken().split("");

        int result = 0;

        for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        }
        
        pw.println(result);
        br.close();
        pw.close();
    }
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Main {
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());

        String[] S_Array = st.nextToken().split("");
        st = new StringTokenizer(br.readLine());
        String[] T_Array = st.nextToken().split("");

        int result = 0;

        for(int i = 0; i < S_Array.length; i++) {
            if(!S_Array[i].equals(T_Array[i])) result++;
        }
        
        pw.println(result);
        br.close();
        pw.close();
    }
}