#include <iostream>
#include <random>

int main() {
  uint64_t in_count = 0;

  uint32_t N = 1000*100;
  for (uint32_t i = 0 ; i < N ; i++) {
    const auto x = static_cast<double>(i)/N;
    for (uint32_t j = 0 ; j < N ; j++) {
      const auto y = static_cast<double>(j)/N;
      if ((x*x + y*y) < 1) {
    in_count++;
      }
    }
  }

  double four = 4;
  std::cout << std::fixed; std::cout.precision(10);
  std::cout << (four*in_count / N) << std::endl;

  return 0;
}