#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
using ld = long double;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
using vll = vector<ll>;
using vi = vector<int>;
const ll mod = (ll)(1e9) + 7LL;
const ll M = 988244353LL;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const ld pi = acos(-1);
ll gcd(ll a, ll b) { return (b ? gcd(b, a % b) : a); }
ll P(ll B, ll power, ll modulo) {
  ll ans = 1LL;
  while (power > 0LL) {
    if (power % 2LL == 1LL) {
      ans = (ans * B) % modulo;
    }
    B = (B * B) % modulo;
    power /= 2LL;
  }
  return ans;
}
bool isPrime(ll n) {
  if (n <= 1LL) {
    return false;
  }
  if (n <= 3LL) {
    return true;
  }
  if (n % 2 == 0LL || n % 3 == 0LL) {
    return false;
  }
  for (ll i = 5LL; (i * i) <= n; i += 6LL) {
    if (n % i == 0LL || n % (i + 2LL) == 0LL) {
      return false;
    }
  }
  return true;
}
void vok() {
  ios_base::sync_with_stdio(false);
  cout.tie(NULL);
  cin.tie(NULL);
}
const int mxN = int(1e5) + 100;
ll run(int l, int r, ll sub, vll &v) {
  if (r < l) {
    return 0;
  }
  if (l == r) {
    return (v[l] != sub);
  }
  int min_ind = l;
  for (int i = l + 1; i < r + 1; i++) {
    if (v[i] < v[min_ind]) {
      min_ind = i;
    }
  }
  ll left = run(l, min_ind - 1, v[min_ind], v);
  ll right = run(min_ind + 1, r, v[min_ind], v);
  ll ret = min((ll)(r - l + 1), left + right + v[min_ind] - sub);
  return ret;
}
void solve() {
  ll n;
  cin >> n;
  vll v(n);
  for (auto &x : v) {
    cin >> x;
  }
  cout << run(0, n - 1, 0, v) << "\n";
}
int main() {
  vok();
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
