package com.company;
import java.util.Scanner;
import java.lang.Math;

public class Main {

    public static void main(String[] args) {
        Scanner num = new Scanner(System.in);
        int a, p;
        double m1, m2, pow2 = 2, pow3 = 3, G;
        a = num.nextInt();
        p = num.nextInt();
        m1 = num.nextDouble();
        m2 = num.nextDouble();
        G = 4 * (Math.pow((Math.PI), pow2)) * Math.pow(a, pow3) / Math.pow(p, pow2) * (m1 + m2);
        System.out.print(G);
    }
}