#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c = 0;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  for (int i = 0; i < n; i++) {
    if (a[i] % a[0] == 0) {
      c++;
    }
  }
  if (c == n) {
    cout << a[0];
  } else {
    cout << -1 << endl;
  }
  return 0;
}
