#include <stdio.h>

float piHesapla(int terim){
	float sonuc=0;
	int i;
	float a=1;
	for(i=0;i<terim/2;i++){
		
		sonuc=sonuc+(4/a)-(4/(a+2));
		a=a+4;
	}
	return sonuc;
}




int main(){
	int a=900;
	float sonuc= piHesapla(a);
	printf("%f",sonuc);
	return 0;
}