#!/usr/bin/env python3

n, i, k = map(int, input().split())
ans = 0.0
P = 0.0
for j in range(0, n+1):
    p = (j / n) ** k - ((j - 1) / n) ** k
    ans += p * (i if j < i else (1 + j) / 2)
    P += p
print(f"{ans:.10}")