#include <bits/stdc++.h>
using namespace std;
int i, n, N, a, b;
double MaxZ = 1e9, MinZ = 0.0;
int main() {
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> N;
    MinZ = max(MinZ, (double)(N * 10.0 / i));
    MaxZ = min(MaxZ, (double)((N + 1) * 10.0) / i);
  }
  a = floor(MinZ * (n + 1) / 10.0);
  b = ceil(MaxZ * (n + 1) / 10.0);
  if (a + 1 >= b) {
    cout << "unique" << endl << a << endl;
  } else {
    cout << "not unique" << endl;
  }
  return 0;
}
