#include <bits/stdc++.h>
using namespace std;
int main() {
    int t; cin >> t;
    while (t--) {
        int x, y; cin >> x >> y;
        int ans = -1;
        for (int k = 1; k <= 100; k++) {
            if (k % x != 0 && k % y != 0) {
                ans = k;
                break;
            }
        }
        cout << ans << endl;
    }
}