#include<bits/stdc++.h>
using namespace std;
#define int long long
const int mo=998244353;
const double pie=acos(-1);
int n,m;
struct comp{
	int p,q;
	friend comp operator+(comp x,comp y){
		return comp{(x.p+y.p),(x.q+y.q)};
	}
};
signed main(){
	cin>>n>>m;
	int k=ceil((double)2.0*m/pie);
	int c=k*(k-1);
	int b=(2*m-((k-1)*2+1));
	comp ans=comp{m>1?(n+1)*n*m:0,0};
	for(int i=1;i<=n;i++){
		int num=(n-i)*2*m;
		int v1=(1+n-i)*(n-i)*m*2ll*m;
		int v2=num*b*2ll*i;
		int v3=2ll*m*b*i;
		ans=ans+comp{(v1+v2+v3),(2ll*(n-i)*c*i+c*i)};
	}
	cout<<fixed<<setprecision(10)<<(double)pie*ans.q+ans.p;
	return 0;
}