#include<bits/stdc++.h>
using namespace std;
#define ll long long
#ifndef ONLINE_JUDGE
    #define dbg(x) cout << #x << ":- " << x << "\n"
#else
    #define dbg(x)
#endif
#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(),x.rend()
#define MOD 1000000007
//-----------------------------------------------------------------------------//
void print(vector<ll>arr){for(int i=0;i<arr.size();i++){cout<<arr[i]<<" ";}
cout<<endl;}
void print(map<ll,ll>mpp){for(auto x:mpp){cout<<x.first<<"-->"<<x.second<<"\n";}
cout<<endl;}
void print(set<ll>s){for(auto x:s){cout<<x<<" ";}cout<<endl;}
//------------------------------------------------------------------------------//

int main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
int t;
cin>>t;
while(t--){
  ll x,y;
  cin>>x>>y;
  ll ans=-1;
  for(int i=1;i<=100;i++){
    if(i%x!=0&&i%y!=0){
        ans=i;
        break;
    }
  }  
  cout<<ans<<"\n";
}

return 0;
 }