code

#include <iostream>
using namespace std;
int main() {
    long long t;
    cin>>t;
    while(t--){
        long long n,m;
        cin>>n>>m;
        long long st=m;
        if(n == 1 && m == 1){
            cout<<1<<endl;
        }
        else if(n == 2 && m == 1){
            cout<<1<<endl;
        }
        else if(m == n-1){
            cout<<2<<endl;
        }
        else if(m < n-1){
            cout<<-1<<endl;
        }
        else if(m > n+(((n-1)*n))/2){
            cout<<-1<<endl;
        }
        else{
            m-=n+1;
            if(m <= 0){
                cout<<2<<endl;
            }
            else{
                m-=n-1;
                if(m<=0){
                    cout<<3<<endl;
                }
                else{
                    m*=2;
                    cout<<(m+n-1)/n+3<<endl;
                }
            }
        }
    }
}