#include <bits/stdc++.h>
using namespace std;
const int maxN = 1000 + 1;
int main() {
  double i, n, a[maxN], x, y, maxi, mini;
  int x2, y2;
  cin >> n;
  maxi = (double)1000 * 1000 * 1000;
  mini = 10;
  for (i = 1; i <= n; ++i) {
    cin >> a[(int)i];
    maxi = min(maxi, ((a[(int)i] + 1) * 10) / i);
    mini = max(mini, (a[(int)i] * 10) / i);
  }
  x = (mini * (n + 1)) / 10;
  x2 = floor(x);
  y = (maxi * (n + 1)) / 10;
  y2 = floor(y);
  if ((double)y2 == y) --y2;
  if (x2 >= y2)
    cout << "unique\n" << x2;
  else
    cout << "not unique\n";
  return 0;
}
