#include<stdio.h>
int nr[1000100];
int main(){
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	int n,i,j,sum=0,min,x;
	
	scanf("%d",&n);
	for(i=0;i<n;++i)
		scanf("%d",&nr[i]);

	for(i=0;i<n;++i){
		while(nr[i]){
			min=10000000;
			for(j=i;nr[j];++j){
				if(nr[j]<min)
					min=nr[j];
			}
			for(x=i;x<j;++x)
				nr[x]-=min;
			sum+=min;
		}
	}
	printf("%d\n",sum);
	fclose(stdin);
	fclose(stdout);
	return 0;
}