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

using namespace std;
int n, m, k;
double ans;

void DFS(vector<int> v)
{
	if(v.size() == n)
	{
		int sum = 0;
		for(int i = 0; i < n; ++i)
		{
			sum += v[i];
		}
		ans += 1.0 * max(1, sum - k) / pow(1.0 * m, n);
		return;
	}
	for(int i = 1; i <= m; ++i)
	{
		v.push_back(i);
		DFS(v);
		v.pop_back();
	}
	return;
}

void solve()
{
	while(cin >> n >> m >> k, n || m || k)
	{
		ans = 0;
		vector<int> v;
		DFS(v);
		printf("%.8f\n", ans);
	}
}

int main()
{
	solve();
	return(0);
}