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