#include <bits/stdc++.h>
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
signed main() {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  long long n;
  cin >> n;
  vector<long long> arr(n);
  for (long long i = 0; i < n; i++) cin >> arr[i];
  function<long long(long long, long long)> solve = [&](long long l,
                                                        long long r) {
    if (r == l) return 0LL;
    if (r == l + 1) return min(1LL, arr[l]);
    long long mn = INT_MAX;
    for (long long i = l; i < r; i++) mn = min(mn, arr[i]);
    for (long long i = l; i < r; i++) arr[i] -= mn;
    long long acc = mn;
    long long prev = l;
    for (long long i = l; i < r; i++) {
      if (arr[i] == 0) {
        acc += solve(prev, i);
        prev = i + 1;
      }
    }
    acc += solve(prev, r);
    return min(acc, r - l);
  };
  cout << solve(0, n) << "\n";
}
