#include<fstream>
using namespace std;

int main()
{
    ifstream in("progresie.in");
    ofstream out("progresie.out");
    unsigned int Tds=1, T, i, N, R;
    unsigned long long Li=1, Ls=1;
    bool faceParte;

    in>>T;

    for(i=1; i<=T; i++)
    {
        in>>N>>R;

        faceParte=false;

        while(faceParte==false)
        {
            Ls=Li+3*Tds;
            Li=Li+2*Tds;
            Tds++;

            if((N-1)*R+Li<=Ls)
                faceParte=true;
        }

        out<<Li<<'\n';
    }

    in.close();
    out.close();
}