#include <bits/stdc++.h>
using namespace std;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout.precision(12);
    cout.setf(ios_base::fixed, ios_base::floatfield);
    
    int64_t n, k;
    cin >> n >> k;
    cout << (n * (n+1) / 2 * k) / 1.0 / ((n+1)*k) << endl;
    
    return 0;
}