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

public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
	}

	public static void solution(String[] args) throws Exception{
		int N = nextInt();

		long[] h = nextLongs();
		long ans =0;
		int st=0;

		while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		}
		System.out.println(ans);
	}





	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

}
 import java.io.*; io.* java import java.util.*; util.* java public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
	}

	public static void solution(String[] args) throws Exception{
		int N = nextInt();

		long[] h = nextLongs();
		long ans =0;
		int st=0;

		while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		}
		System.out.println(ans);
	}





	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

} Main final static long MOD = 1000000007; MOD 1000000007 public static String[] Ws = null; Ws null public static int wsIndx = 0; wsIndx 0 public static BufferedReader in = null; in null public static long cnt=0; cnt 0 public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
	} main {
		solution(args);
		if(in!=null){
			in.close();
		}
	} solution(args) solution args if(in!=null){
			in.close();
		} in!=null in null {
			in.close();
		} in.close() in.close in String[] args args public static void solution(String[] args) throws Exception{
		int N = nextInt();

		long[] h = nextLongs();
		long ans =0;
		int st=0;

		while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		}
		System.out.println(ans);
	} solution {
		int N = nextInt();

		long[] h = nextLongs();
		long ans =0;
		int st=0;

		while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		}
		System.out.println(ans);
	} int N = nextInt(); N nextInt() nextInt long[] h = nextLongs(); h nextLongs() nextLongs long ans =0; ans 0 int st=0; st 0 while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		} st!=N st N {
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		} for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			} int i=st; int i=st; i st i<N i N i++ i++ i {
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			} {
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			} if(h[st]==0){
					st=st+1;
				}else{
					break;
				} h[st]==0 h[st] h st 0 {
					st=st+1;
				} st=st+1 st st+1 st 1 {
					break;
				} break; long min=Long.MAX_VALUE; min Long.MAX_VALUE Long Long.MAX_VALUE int eIdx=N; eIdx N for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			} int i=st; int i=st; i st i<N i N i++ i++ i {
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			} {
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			} if(h[i]==0){
					eIdx=i;
					break;
				} h[i]==0 h[i] h i 0 {
					eIdx=i;
					break;
				} eIdx=i eIdx i break; min=Math.min(min, h[i]) min Math.min(min, h[i]) Math.min Math min h[i] h i for(int i=st;i<eIdx;i++){
				h[i]-=min;
			} int i=st; int i=st; i st i<eIdx i eIdx i++ i++ i {
				h[i]-=min;
			} {
				h[i]-=min;
			} h[i]-=min h[i] h i min if(min!=Long.MAX_VALUE){
				ans+=min;
			} min!=Long.MAX_VALUE min Long.MAX_VALUE Long Long.MAX_VALUE {
				ans+=min;
			} ans+=min ans min System.out.println(ans) System.out.println System.out System System.out ans String[] args args public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	} check {
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	} if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		} in == null in null {
			in = new BufferedReader(new InputStreamReader(System.in));
		} in = new BufferedReader(new InputStreamReader(System.in)) in new BufferedReader(new InputStreamReader(System.in)) if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		} Ws==null || Ws.length<=wsIndx Ws==null Ws null Ws.length<=wsIndx Ws.length Ws Ws.length wsIndx {
			Ws = in.readLine().split(" ");
			wsIndx=0;
		} Ws = in.readLine().split(" ") Ws in.readLine().split(" ") in.readLine().split in.readLine() in.readLine in " " wsIndx=0 wsIndx 0 public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	} nextInt {
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	} check() check return Integer.parseInt(Ws[wsIndx++]); Integer.parseInt(Ws[wsIndx++]) Integer.parseInt Integer Ws[wsIndx++] Ws wsIndx++ wsIndx public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	} nextLong {
		check();
		return Long.parseLong(Ws[wsIndx++]);
	} check() check return Long.parseLong(Ws[wsIndx++]); Long.parseLong(Ws[wsIndx++]) Long.parseLong Long Ws[wsIndx++] Ws wsIndx++ wsIndx public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	} nextString {
		check();
		return Ws[wsIndx++];
	} check() check return Ws[wsIndx++]; Ws[wsIndx++] Ws wsIndx++ wsIndx public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} nextInts {
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} check() check int[] tmp = new int[Ws.length]; tmp new int[Ws.length] Ws.length Ws Ws.length for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		} int i=0; int i=0; i 0 i<tmp.length i tmp.length tmp tmp.length i++ i++ i {
			tmp[i]=Integer.parseInt(Ws[i]);
		} {
			tmp[i]=Integer.parseInt(Ws[i]);
		} tmp[i]=Integer.parseInt(Ws[i]) tmp[i] tmp i Integer.parseInt(Ws[i]) Integer.parseInt Integer Ws[i] Ws i wsIndx=Ws.length wsIndx Ws.length Ws Ws.length return tmp; tmp public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} nextLongs {
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	} check() check long[] tmp = new long[Ws.length]; tmp new long[Ws.length] Ws.length Ws Ws.length for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		} int i=0; int i=0; i 0 i<tmp.length i tmp.length tmp tmp.length i++ i++ i {
			tmp[i]=Long.parseLong(Ws[i]);
		} {
			tmp[i]=Long.parseLong(Ws[i]);
		} tmp[i]=Long.parseLong(Ws[i]) tmp[i] tmp i Long.parseLong(Ws[i]) Long.parseLong Long Ws[i] Ws i wsIndx=Ws.length wsIndx Ws.length Ws Ws.length return tmp; tmp public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	} nextStrings {
		check();
		wsIndx=Ws.length;
		return Ws;
	} check() check wsIndx=Ws.length wsIndx Ws.length Ws Ws.length return Ws; Ws public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
	}

	public static void solution(String[] args) throws Exception{
		int N = nextInt();

		long[] h = nextLongs();
		long ans =0;
		int st=0;

		while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		}
		System.out.println(ans);
	}





	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

} public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
	}

	public static void solution(String[] args) throws Exception{
		int N = nextInt();

		long[] h = nextLongs();
		long ans =0;
		int st=0;

		while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		}
		System.out.println(ans);
	}





	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

} Main
import java.io.*;
import java.util.*;

public class Main {

	final static long MOD = 1000000007;
	public static String[] Ws = null;
	public static int wsIndx = 0;
	public static BufferedReader in = null;
	public static long cnt=0;
	public static void main(String[] args) throws Exception {
		solution(args);
		if(in!=null){
			in.close();
		}
	}

	public static void solution(String[] args) throws Exception{
		int N = nextInt();

		long[] h = nextLongs();
		long ans =0;
		int st=0;

		while(st!=N){
			for(int i=st;i<N;i++){
				if(h[st]==0){
					st=st+1;
				}else{
					break;
				}
			}
			long min=Long.MAX_VALUE;
			int eIdx=N;
			for(int i=st;i<N;i++){
				if(h[i]==0){
					eIdx=i;
					break;
				}
				min=Math.min(min, h[i]);
			}
			for(int i=st;i<eIdx;i++){
				h[i]-=min;
			}
			if(min!=Long.MAX_VALUE){
				ans+=min;
			}
		}
		System.out.println(ans);
	}





	public static void check() throws Exception{
		if(in == null){
			in = new BufferedReader(new InputStreamReader(System.in));
		}
		if(Ws==null || Ws.length<=wsIndx){
			Ws = in.readLine().split(" ");
			wsIndx=0;
		}
	}
	public static int nextInt()throws Exception{
		check();
		return Integer.parseInt(Ws[wsIndx++]);
	}

	public static long nextLong()throws Exception{
		check();
		return Long.parseLong(Ws[wsIndx++]);
	}

	public static String nextString()throws Exception{
		check();
		return Ws[wsIndx++];
	}

	public static int[] nextInts()throws Exception{
		check();
		int[] tmp = new int[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Integer.parseInt(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static long[] nextLongs()throws Exception{
		check();
		long[] tmp = new long[Ws.length];
		for(int i=0;i<tmp.length;i++){
			tmp[i]=Long.parseLong(Ws[i]);
		}
		wsIndx=Ws.length;
		return tmp;
	}

	public static String[] nextStrings()throws Exception{
		check();
		wsIndx=Ws.length;
		return Ws;
	}

}

