#include <bits/stdc++.h>
using namespace std;
int main()
{
    int t;
    cin >> t;
    for (int i = 0; i < t; i++)
    {
        int a, b, lcd;
        cin >> a >> b;
        int mx = max(a, b);
        lcd = -1;
        for (int j = 2; j <= mx; j++)
        {
            if (a % j == 0 && b % j == 0)
            {
                lcd = j;
                break;
            }
        }
        cout << lcd << endl;
    }

    return 0;
}