#include <bits/stdc++.h>
using namespace std;
using PP = pair<long, long>;
const int INF = 1e9;
template <class T> T Next() { T buf; cin >> buf; return buf; }

int n;
int v[26];
char a[500][500];
bool impossible() {
  int sum = 0;
  for (int i = 0; i < n; ++i) {
    sum += v[i] * v[i];
  }
  for (int k = 1; k <= 500; ++k) {
    if (k * k == sum) return false;
  }
  return true;
}

void sub() {
  if (impossible()) {
    cout << -1 << endl;
    return;
  }
  cout << "??" << endl;
  return;
}

int main() {
  cin >> n;
  for (int i = 0; i < n; ++i) cin >> v[i];
  sub();
  return 0;
}