C++ :

#include <bits/stdc++.h>
using namespace std;
int main()
{
	//freopen("F:\\QQDownlaod\\Laputa\\2015.3.23\\my2\\data.in","r",stdin);
	//freopen("F:\\QQDownlaod\\Laputa\\2015.3.23\\my2\\data.out","w",stdout);
	const double PI = acos(-1.0);
	int d,l;
	while(~scanf("%d%d",&d,&l)){
		double p=1.0-(2.0*l)/(PI*d);
		printf("%.2f\n",p);
	}
	return 0;
}