diametro

import java.util.Scanner;


public class area {

    public static void main(String[] args) {
        Scanner input=new Scanner(System.in);
        int n=input.nextInt();

        double A=0;
        for(int i=0;i<n;i++){
            double L=input.nextLong();
            double D=input.nextLong();
            A=(L*D)+(Math.PI*((D/2)*(D/2)));

            System.out.println(A);

        }
    }

}