#include <iostream.h>

double PiOver2(double Denom, double Pi){
	if(Denom != 19999)
		return(PiOver2(Denom+2,Pi * (Denom+1)/Denom * (Denom+1)/(Denom+2)));
	else
		return(Pi);
}

int main(){
cout<< PiOver2(1,1) << endl;
return(0);
}