#include<stdio.h>
#define NM 1000001
int v[NM+1];

int main(){
freopen("operatii.in","r",stdin);
freopen("operatii.out","w",stdout);
int n,i,j,k,nr=0;
scanf("%d",&n);
for(i=1;i<=n;++i) scanf("%d",&v[i]);
i=1;
do{
	while(i<=n&&!v[i]) i++;
	if(i>n) break;
	if(v[i]){
		j=i;
		while(j<=n&&v[j]){
			v[j]--;
			j++;
			}
		nr++;
		}
	}while(i<=n);
printf("%d",nr);
return 0;
}