#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 i=1;i<=100;i++){
            if(i%x!=0 && i%y!=0){
                ans=i;
                break;
            }
        }
        cout<<ans<<endl;
    }
}