#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n, even = 0, odd = 0;
  cin >> n;
  long long int a[n];
  for (long long int i = 0; i < n; i++) cin >> a[i];
  if (n == 1)
    cout << a[0] << "\n";
  else {
    sort(a, a + n);
    long long int flag = 0;
    for (long long int i = 1; i < n; i++) {
      if (a[i] % a[0] != 0) {
        flag = 1;
        break;
      }
    }
    if (flag == 0)
      cout << a[0] << "\n";
    else
      cout << "-1"
           << "\n";
  }
  return 0;
}
