#include<bits/stdc++.h>
#define double long double
#define int long long
using namespace std;
const int maxn=1e7+5;
const int mod=998244353;
const double PI=acos(-1);
int n,m;
double f[maxn],g[maxn],pref,preg;
int qpow(int a,int b){
	int ans=1;
	while(b){
		if(b&1)(ans*=a)%=mod;
		(a*=a)%=mod;
		b>>=1;
	}
	return ans;
}
signed main(){
//	freopen("a.in","r",stdin);
//	freopen("a.out","w",stdout);
	cin>>n>>m;
	if(n==1&&m==1){
		cout<<2;
		return 0;
	}
	int tot=0;
	double lim=(double)2*m/PI;
	int o=qpow(m,mod-2);
	for(int i=1;i<=m;i++){
		int k=i;
		if((double)k*PI>2*m){
			f[1]+=2;
		}
		else g[1]+=(double)i/m;
	}
	f[1]=(2*f[1]-2)*m;g[1]=g[1]*2*m;
	pref=f[1],preg=g[1];
	for(int i=2;i<=n;i++){
		f[i]=i*f[1],g[i]=i*g[1];
		f[i]=(f[i]+(i-1)*4*m*m+(i-1)*f[1]+f[i-1]);
		g[i]=(g[i]+(g[1]*(i-1))+g[i-1]);
		pref=(pref+f[i]);
		preg=(preg+g[i]);
	}
	cout<<setprecision(10)<<(double)pref+(m!=1)*m*(n+1)*n+(double)preg*PI;
//	printf("%.10lf\n",(double)pref+m*(n+1)*n+(double)preg*PI);
//	printf("%.10lf",(double)(preg)*PI);
}