#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:136777216")
using namespace std;
int bits(int x) { return x == 0 ? 0 : 1 + bits(x & (x - 1)); }
bool v[1111111];
int main() {
  int n, t, m = 0;
  cin >> n;
  for (int(i) = 0; (i) < (n); (i)++) {
    cin >> t;
    v[t] = 1;
    m = max(m, t);
  }
  int k = 0;
  double low = 0., high = 1e10;
  for (int i = 1; i <= m; i++) {
    if (v[i]) {
      high = min(high, 10. * (1 + i) / (1 + k));
      k++;
    } else {
      low = max(low, 10. * (1 + i) / (1 + k));
    }
  }
  int can1 = (int)(((1 + n) * low - 10 * m) / 10);
  int can2 = (int)(((1 + n) * high - 10 * m - 1e-6) / 10);
  if (can1 == can2)
    printf("unique\n%d", m + can1);
  else
    printf("not unique");
  return 0;
}
