#include <iostream.h>

double PiOver4(double Denom, double Pi){
	if(Denom != 9999)
		return(PiOver4(Denom+4,Pi + 1/(Denom+2) - 1/(Denom)));
	else
		return(1 + Pi);
}

int main(){
cout<< PiOver4(3,0) << endl;
return(0);
}