#include <bits/stdc++.h>
using namespace std;
long long n, ans, h[5005];
void f(long long l,long long r){
	if(r < l) return;
	else if(r == l && h[r]){
		ans++;
		return;
	}
	long long minn = 0xfffffff, k;
	for(long long i = l; i <= r; i++)
		if(h[i] < minn){
			minn = h[i];
			k = i;
		}
	for(long long i = l; i <= r; i++)
		h[i] -= minn;
	ans += minn;
	f(l, k - 1);
	f(k + 1, r);
}
int main(){
	scanf("%lld", &n);
	for(long long i = 1; i <= n; i++)
		scanf("%lld", &h[i]);
	f(1, n);
	printf("%lld", ans);
	return 0;
}