#include<bits/stdc++.h>

using namespace std;

double funtion(double x,int n){
    if(n==0)
        return 1;
    if(n==1) return x;
    return ((2*n-1)*x-funtion(x,n-1)-(n-1)*funtion(x,n-2))/n;
}

int main(){
    int n;
    double x;
    while(cin>>n>>x){
        cout<<funtion(x,n)<<endl;
    }
}