#include
#include
void main()
{
int s;
float n,t,pi;
s=1,pi=0,n=t=1.0;

do
{
pi+=t;
n+=2;
s=-s;
t=s/n;
}while(fabs(t)>1e-4);

pi*=4;
printf("pi=%.4f\n",pi);
}