#include <stdio.h>
#define N 1000
main(void)
{
  long i;
  long a=0;
  long x=0, y=N;
  for (i=0; i<2*N-1; i++) {
    if ((x+1)*(x+1) + y*y < N*N) {
      x++;
      a = a + y;
    } else {
      y--;
    }
  }
  printf("pi is nearly %.10f\n", ((double) a)/(N*N)*4);
}