#include <bits/stdc++.h>
inline int gcd(int a, int b) {
  while (b) {
    int t = b;
    b = a % b;
    a = t;
  }
  return a;
}
class Fraction {
 public:
  int c, d;
  void simp() {
    int g = gcd(c, d);
    c /= g;
    d /= g;
  }
  Fraction(int ci) : c(ci), d(1) {}
  Fraction(int ci, int di) : c(ci), d(di) { simp(); }
  const bool operator<(const Fraction &b) const {
    return (long long)c * b.d < (long long)b.c * d;
  }
};
int n;
int s[1050];
Fraction a1(1, 1), a2(2000000, 1);
inline Fraction min(Fraction a, Fraction b) { return a < b ? a : b; }
inline Fraction max(Fraction a, Fraction b) { return a < b ? b : a; }
inline void solve() {
  for (int i = 0; i < n; i++) {
    a1 = max(a1, Fraction(s[i], i + 1));
    a2 = min(a2, Fraction(s[i] + 1, i + 1));
  }
  int x1 = (long long)a1.c * (n + 1) / a1.d;
  int x2 = ((long long)a2.c * (n + 1) - 1) / a2.d;
  if (x1 == x2) {
    puts("unique");
    printf("%d\n", x1);
  } else {
    puts("not unique");
  }
}
int main(void) {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", s + i);
  solve();
  return 0;
}
