#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1 << 28;
constexpr long long mod = 1000000007LL;
//constexpr long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;


void solve() {
	ll n, m, k; scanf("%lld %lld %lld", &n, &m, &k); if (n == 0 and m == 0 and k == 0) exit(0);
	vector<vector<double>> dp(n + 1, vector<double>(n * m + 1));
	dp[0][0] = 1;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j <= n * m; j++) {
			if (dp[i][j] < 1e-14) continue;
			for (int k = 1; k <= m; k++) {
				if (j + k <= n * m) {
					dp[i + 1][j + k] += dp[i][j] / (double)m;
				}
			}
		}
	}
	double res = 0;
	for (int i = 1; i <= n * m; i++) {
		res += dp[n][i] * max(1LL, i - k);
	}
	printf("%.12f\n", res);
}

int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	int kkt = 89;
	while (kkt) {
		solve();
	}
	return 0;
}
