#include <iostream>
using namespace std;

int main(){
  int t;
  cin>>t;
  while(t--){
    int x,y;
    cin>>x>>y;
   if(x==1||y==1){
    cout<<"-1"<<endl;
   }
    else if(x==17)
        cout<<"19"<<endl;
    else cout<<"17"<<endl;
  }
}