#include <iostream>
#include <random>

double draw(double a, double b) {
  static std::default_random_engine engine(std::random_device{}());
  std::uniform_real_distribution<double> uniform_dist(a, b);
  return uniform_dist(engine);
}

double pi(unsigned N) {
  std::size_t cnt = 0;
  for (std::size_t i = 0; i < N; ++i) {
    const double x = draw(-1., 1.);
    const double y = draw(-1., 1.);
    if (x * x + y * y <= 1) {
      ++cnt;
    }
  }
  return 4. * cnt / N;
}

int main()
{
  for (unsigned N = 10; N < 1e9; N *= 10) {
    std::cout << pi(N) << std::endl;
  }
}