#include <iostream>
#include <vector>
#include <algorithm>
#define rep(i, a, n) for(int i = a; i < n; i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

int main()
{
    double n, k;
    cin >> n >> k;
    double ans = 0;
    rep(i, 0, n+1){
        ans += i*k/((n + 1)*k);
    }
    cout << ans << endl;
    return 0;
}