#include <bits/stdc++.h>
using namespace std;
const int MaxN = 1005;
const double eps = 1e-9;
int n;
double c, s = 10.0, t = 1e20;
inline int calc(double v, int lim) {
  int ans = (int)((n + 1) * v / 10.0 + eps);
  if (lim == 1 && (ans * 10.0 - (n + 1) * v > -eps)) return ans - 1;
  return ans;
}
int main() {
  scanf("%d", &n);
  for (int k = 1; k <= n; ++k) {
    scanf("%lf", &c);
    s = max(s, c * 10.0 / k);
    t = min(t, (c + 1) * 10.0 / k);
  }
  if (calc(s, 0) != calc(t, 1))
    puts("not unique");
  else {
    puts("unique");
    printf("%d\n", calc(s, 0));
  }
  return 0;
}
