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

int main() {
  int n, k;
  cin >> n >> k;
  double ans = 0;
  for (int i = 0; i < n; i++) {
    ans += double((k*(i+1))) / ((n+1)*k);
  }
  cout << fixed << setprecision(6) << ans << endl;
}