#include <iostream>
#include <cmath>

using namespace std;
int n, m, k;
int ans = 0;

void dfs(int a, int b)
{
	if(a == 0)
	{
		ans += b - k <= 0 ? 1 : b - k;
		//cout << ans << endl;
	}
	else
	{
		for(int i = 1; i <= m; ++i)
		{
			dfs(a - 1, b + i);
		}
	}
}

void solve()
{
	while(cin >> n >> m >> k, n || m || k)
	{
		ans = 0;
		dfs(n, 0);
		printf("%.8f\n", ans / pow((double)m, n));
	}
}

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