#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, p = 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) {
      p = 1;
      break;
    }
  }
  if (p == 1) {
    cout << -1;
  } else {
    cout << a[0];
  }
}
