/*
 * author:  ADMathNoob
 * created: 05/08/24 11:16:09
 * problem: https://qoj.ac/problem/2303
 */

/*
Comments about problem:


*/

#include <bits/stdc++.h>

using namespace std;

#ifdef _DEBUG
#include "debug.h"
#else
#define debug(...) 42
#endif

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n, i, k;
  cin >> n >> i >> k;
  double prob_untouched = pow(1.0 * (i - 1) / n, k);
  double ans = prob_untouched * i;
  for (int mx = i; mx <= n; mx++) {
    double p = pow(1.0 * mx / n, k) - pow(1.0 * (mx - 1) / n, k);
    ans += p * (1.0 + mx) / 2;
  }
  cout.precision(10);
  cout << fixed;
  cout << ans << '\n';
  return 0;
}