#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;
}