package com.study.demo;
import java.util.Scanner;

public class test5 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int c = scanner.nextInt();
        double pi = 3.1415926535;
        double area = a * b * c + a * c + (pi * c * c) / 4;
        System.out.printf("%.3f\n", area / 10000);
    }
}