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

int main() {
  int n, k;
  cin >> n >> k;
  int m = (n + 1) * k;
  double ans = 0;
  for (int i = 0; i <= n; ++i) {
    double one = (double)1 / m * i;
    ans += (one * k);
  }
  cout << fixed << setprecision(10) << ans << '\n';
  return 0;
}