#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1010 + 1;
const double EPS = 1E-8;
int n;
double a[MAXN], low[MAXN], high[MAXN], mmin, mmax;
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%lf", &a[i]);
    if (i) {
      low[i] = 10 * a[i] / (i + 1);
      high[i] = 10 * (a[i] + 1) / (i + 1);
      mmin = max(mmin, low[i]);
      mmax = min(mmax, high[i]);
    } else {
      low[i] = 10 * a[i];
      high[i] = 10 * (a[i] + 1);
      mmin = low[i];
      mmax = high[i];
    }
  }
  mmin = (n + 1) * mmin / 10;
  mmax = (n + 1) * mmax / 10;
  int res = (int)floor(mmin + EPS);
  if (res - EPS < mmin && mmax < res + 1 + EPS) {
    puts("unique");
    printf("%d\n", res);
  } else {
    puts("not unique");
  }
  return 0;
}
