#include <bits/stdc++.h>
using namespace std;
long long n;
const long long N = 5005;
long long a[N];
long long dp[N][N];
long long dfs(long long i, long long j, long long h) {
  if (i > j) return 0;
  long long mn = min_element(a + i, a + j + 1) - a;
  long long ans = j - i + 1;
  ans = min(ans, dfs(i, mn - 1, a[mn]) + dfs(mn + 1, j, a[mn]) + a[mn] - h);
  return ans;
}
void solve() {
  cin >> n;
  for (long long i = 0; i < (n); i++) cin >> a[i];
  memset(dp, (long long)(-1), sizeof(dp));
  cout << dfs(0, n - 1, 0);
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  while (t--) {
    solve();
  }
}
