#include <bits/stdc++.h>
using namespace std;

bool is_sq(int a) {
    int l = 0, r = 501;
    while (l < r - 1) {
        int m = (l + r) / 2;
        if (m * m > r) {
            r = m;
        } else {
            l = m;
        }
    }
    return l * l == a;
}

int main() {
    int n;
    cin >> n;
    vector<int> as(n);
    int sum = 0;
    for (int i = 0; i < n; i++) {
        int a;
        cin >> a;
        as[i] = a;
        sum += a * a;
    }
    if (is_sq(sum)) {
        cout << -1 << endl;
    } else {
        cout << -1 << endl;
    }
}