#include <vector>
#include <numeric>
#include <iostream>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tt;
  cin >> tt;
  while (tt--) {
    int n, m;
    cin >> n >> m;
    n = gcd(n, m);
    if (n == 1) {
      cout << -1 << '\n';
    } else {
      m = n;
      for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) {
          m = i;
          break;
        }
      }
      cout << m << '\n';
    }
  }
  return 0;
}