#include <bits/stdc++.h>
const int MaxN = 5000;
using namespace std;
int a[MaxN + 5];
long long res;
long long dp[MaxN + 5][MaxN + 5];
int n;
long long Solve(int l, int r) {
  if (l > r) return 0;
  if (l == r) {
    return a[l] != 0;
  }
  int MinPos = l;
  for (int i = l; i <= r; i++)
    if (a[i] < a[MinPos]) MinPos = i;
  long long Min = a[MinPos];
  for (int i = l; i <= r; i++) a[i] -= Min;
  return min((long long)r - l + 1,
             Solve(l, MinPos - 1) + Solve(MinPos + 1, r) + Min);
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (int i = 1; i <= n; i++)
    for (int j = i; j <= n; j++) dp[i][j] = -1;
  res = Solve(1, n);
  printf("%lld\n", res);
  return 0;
}
