#include <cstdio>
using namespace std;
#define ll long long
void solve()
{
    ll n, m;
    scanf("%lld %lld", &n, &m);
    ll smaller = (n < m) ? n : m;
    for (ll i = 2; i <= smaller; ++i)
    {
        if (n % i == 0 && m % i == 0)
        {
            printf("%lld\n", i);
            return;
        }
    }
    printf("-1\n");
}

int main()
{
    int t;
    scanf("%d", &t);
    while (t--)
        solve();
    return 0;
}