#include <iostream>
#include <iomanip>

const double PI = 3.14;

int main() {
    int r1, r2;
    std::cin >> r1 >> r2;

    double outer_area = PI * r1 * r1;
    double inner_area = PI * r2 * r2;

    double area = outer_area - inner_area;

    std::cout << std::fixed << std::setprecision(2) << area << std::endl;

    return 0;
}    
/**************************************************************
	Problem: 1338
	User: fuyijun
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/