#include <bits/stdc++.h>
using namespace std;
inline long long int mod(long long int a, long long int b,
                         long long int x = 1000000007) {
  long long int res = 1;
  a = a % x;
  while (b > 0) {
    if (b & 1) {
      res = (res * a) % x;
    }
    b = b >> 1;
    a = (a * a) % x;
  }
  return res;
}
inline long long int gcd(long long int a, long long int b) {
  long long int r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline long long int lcm(long long int a, long long int b) {
  return a / gcd(a, b) * b;
}
inline long long int left(long long int i) { return (i << 1); }
inline long long int right(long long int i) { return ((i << 1) + 1); }
const int maxn = 1e5 + 5;
const int maxx = 1e6 + 5;
const int logn = 316;
double ans[100005];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int n, k;
  cin >> n >> k;
  long long int m = min(650ll, n);
  for (long long int i = 1; i <= n; i++) {
    for (long long int j = 1; j <= m; j++) {
      ans[j] =
          1.0 / k / (j + 1) * (j * ans[j] + ans[j + 1] + j * (j + 3.0) / 2.0) +
          1.0 * (k - 1) / k * ans[j];
    }
  }
  cout << fixed << setprecision(12);
  cout << ans[1] * k << "\n";
  return 0;
}
