#include <bits/stdc++.h>
#include <regex>
using namespace std;
#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(a) begin(a),end(a)
#define MS(m,v) memset(m,v,sizeof(m))
#define D10  fixed<<setprecision(10)
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> P;
typedef complex<double> Point;
typedef long long ll;
const int INF = 1145141919;
const int MOD = 100000007;
const double EPS = 1e-10;
const double PI = acos(-1.0);
struct edge
{
	int from, to, cost;
	bool operator < (const edge& e) const { return cost < e.cost; }
	bool operator > (const edge& e) const { return cost > e.cost; }
};
///*************************************************************************************///
///*************************************************************************************///
///*************************************************************************************///

int n, m, k;
double mod;

double solve(int i, int sum)
{
	if (i == n)
	{
		if (sum <= k) return 1 / mod;
		return (sum-k) / mod;
	}
	double res = 0;
	FOR(j, 1, m + 1)
	{
		res += solve(i + 1, sum + j);
	}
	return res;
}
int main()
{
	while (cin >> n >> m >> k, n)
	{
		mod = pow(m, n);
		cout << D10 << solve(0, 0) << endl;
	}
	return 0;
}