#include <bits/stdc++.h>
using namespace std;
int a[103];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
  }
  sort(a, a + n);
  for (int i = 1; i < n; ++i) {
    if (a[i] > a[i - 1]) {
      cout << a[i];
      return 0;
    }
  }
  cout << "NO";
}
