#include <iostream>
#include <vector>

using namespace std;

int main(){
    int t;
    cin>>t;
    vector<bool> prime(10010010,true);
    prime[0]=false;
    prime[1]=false;

    for(int i=2;i*i<=10010010;i++){
        if(!prime[i]) continue;
        for(int j=i*i;j<=10010010;j+=i){
            prime[j]=false;
        }
    }
    for(int i=0;i<t;i++){
        long long a,p;
        cin>>a>>p;
        if(prime[p]){
            cout<<-1<<endl;
            continue;
        }
        if(a==p){
            cout<<0<<endl;
        }else{
            cout<<1<<endl;
        }

    }
    return 0;
}