#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;
    }
    
}