#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;

#define nl "\n"

int main () {

    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    ll t; cin>>t;
    while (t--) {
        ll x,y;
        cin>>x>>y;
        ll a=-1;
        for(ll i=1; i<=100; i++){
            if(i%x!=0 && i%y!=0) {
                a=i;
                break;
            }
        }
        cout<<a<<nl;
    }

    return 0;
}