// AOJ 1286: Expected Allowance
// 2017.10.13 bal4u@uu

#include <stdio.h>
#include <math.h>

int m, k;

int combi(int n, int s)
{
	int i, t;

	if (n == 0)	return s-k > 0 ? s-k : 1;
	for (t = 0, i = 1; i <= m; i++) t += combi(n-1, s+i);
	return t;
}

int main()
{
	int n;

	while (scanf("%d%d%d", &n, &m, &k) && n > 0)
		printf("%.8lf\n", combi(n, 0) / pow(m, n));
	return 0;
}