import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int ans=0;
		int a=scan.nextInt();
		int b[]=new int[a];
		for(int i=0;i!=a;i++) {
			b[i]=scan.nextInt();
		}
		int i=0;
		int k=0;
		for(int o=0;;o++) {
			if(o==a) {
				k=1;
				break;
		}
		if(b[o]!=0) {
			break;
		}
		}
		if(k==1) {
			System.out.println(0);
		}
		else {
			k=0;
		for(;;) {
			if(k==1) {
				break;
			}
			if(b[i]!=0) {
				for(int j=i;;j++) {
					if(j==a) {
						break;
					}
					if(b[j]==0) {
						break;
					}
					b[j]--;
				}
				ans++;
				i=0;
				for(int j=0;j!=a+1;j++) {
					if(j==a) {
						k=1;
						break;
				}
				if(b[j]!=0) {
					break;
				}
					
				}
				continue;
			}
			
			i++;
		}
		System.out.println(ans);
	}
		}
	}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz