---

#include <cmath>
#include <iomanip>
#include <iostream>

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

  std::cout << std::fixed << std::setprecision(6) << 3.14 * std::pow(r2, 2) - 3.14 * std::pow(r1, 2);

  return 0;
}