#include  <stdio.h>
#include  <math.h>
int main(void)
{
    float t=1.0, sum =0;
    int n=1 , a=1;
    while (fabs(t)>1e-4)
    {
        sum = sum+ t ;
        n = n +2;
        a=-a;
        t = a*1.0/n;
    }    
    printf ("Π=%f\n",4*sum);
    return 0;
}