#include <bits/stdc++.h>
using namespace std;
int ToInt(string& s, int len) {
  int r = 0;
  for (int i = 0, max_ = (len); i < max_; ++i) {
    r *= 10;
    r += s[i] - '0';
  }
  return r;
}
int GCD(int a, int b) { return b != 0 ? GCD(b, a % b) : a; }
int LCM(int a, int b) { return a * (b / GCD(a, b)); }
long long Pow(long long n, long long e) {
  if (e == 0) return 1;
  if (e == 1)
    return n;
  else if (e & 1) {
    long long t = Pow(n, e / 2);
    return n * t * t;
  } else {
    long long t = Pow(n, e / 2);
    return t * t;
  }
}
int v[100005];
int main() {
  int N;
  scanf("%d", &N);
  for (int i = 0, max_ = (N); i < max_; ++i) scanf("%d", &v[i]);
  if (N == 1) {
    printf("%d\n", v[0]);
  } else {
    int gcd = GCD(v[0], v[1]);
    for (int i = (2), max_ = (N); i < max_; ++i) gcd = GCD(gcd, v[i]);
    for (int i = 0, max_ = (N); i < max_; ++i)
      if (v[i] == gcd) {
        printf("%d\n", gcd);
        return 0;
      }
    printf("-1\n");
  }
  return 0;
}
