#include <iostream>
#include <math.h>

using namespace std;

int main ()
{
  double n, k;
  int i;
  cin >> n >> i >> k;
  double ans = (i - 1) * pow ((i - 1) / n, k);

  double sum = 0;
  for (int j = i; j < n; j++)
    sum = sum + pow (j / n, k);

  ans = (ans + n + 1 - sum) / 2;

  cout.precision (12);
  cout << ans;

  return 0;
}