#include <bits/stdc++.h>
using namespace std;
int a[1010];
int check(double ans, int n) {
  double now = 0;
  for (int i = 0; i <= n; i++) {
    if (now - 10 < 0) now += ans;
    now -= 10;
  }
  return n + 1 + (int)(now / 10);
}
int main() {
  int n;
  while (scanf("%d", &n) == 1) {
    for (int i = 0; i < n; i++) scanf("%d", &a[i]);
    double low = 10, high = 1e60;
    for (int i = 0; i < n; i++) {
      double tl = a[i] * 10;
      double tr = (a[i] + 1) * 10;
      low = max(low, tl / (i + 1));
      high = min(high, tr / (i + 1));
    }
    high -= 1e-8;
    int ans1 = check(low, a[n - 1]);
    int ans2 = check(high, a[n - 1]);
    if (ans1 == ans2) {
      puts("unique");
      printf("%d\n", ans1);
    } else
      puts("not unique");
  }
  return 0;
}
