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