#include <stdio.h>

static long num_steps = 100000;
double step;

int main()
{
  int i;
  double x, pi, sum = 0.0;
  step = 1.0/(double) num_steps;

  for (i=1; i<= num_steps; i++) {
    x = (i-0.5)*step;
    sum = sum + 4.0/(1.0+x*x);
  }
  pi = step * sum;

  printf("pi = %.16f\n",pi);
}