#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>


typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;





int main()
{

    int Q;
    Q = 1;
    //cin >> Q;

    while (Q--) {
        int n, k;
        cin >> n >> k;
        double a = 0;
        double p = n + 1;
        p *= k;
        for (int i = 0; i <= n; i++) {
            a += i  * k/p;
        }
        cout << setprecision(20);
        cout << a << endl;
    }
    return 0;
}