#include <bits/stdc++.h>
double min(double a, double b) {
  if (a < b) {
    return a;
  } else {
    return b;
  }
}
double max(double a, double b) {
  if (a > b) {
    return a;
  } else {
    return b;
  }
}
int main() {
  int n, i;
  int a[1000];
  double m1 = 10, m2 = 1e9;
  scanf("%d", &n);
  for (i = 0; i < n; i++) scanf("%d", &a[i]);
  for (i = 0; i < n; i++) {
    m1 = max(m1, (double)a[i] * 10 / (i + 1) + 1e-6);
    m2 = min(m2, (double)(a[i] + 1) * 10 / (i + 1) - 1e-6);
  }
  if ((int)(m1 * (n + 1)) / 10 == (int)(m2 * (n + 1)) / 10) {
    puts("unique");
    printf("%d\n", (int)(m1 * (n + 1)) / 10);
  } else {
    puts("not unique");
  }
  return 0;
}
