#include<iostream>
#include<cstdio>
#include<string>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
using namespace std;
typedef long long ll;
const ll MOD = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
const double EPS = 1e-9;
typedef pair<int, int> P;
typedef unsigned int ui;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
int main() {
	int n, m, k;
	while (cin >> n >> m >> k, n) {
		if (n > 1) {
			double r = 1; double out = 0;
			rep(i, n) {
				r *= m;
			}
			ll cnt = 0; int dp[1000] = {};
			dp[0] = 1;
			rep(i, n) {
				for (int j = 999; j >= 0; j--) {
					rep1(k, m) {
						if (j + k < 1000) {
							dp[j + k] += dp[j];
						}
					}
					dp[j] = 0;
				}
			}
			rep(i, 1000) {
				int x = i - k;
				if (x <= 0)x = 1;
				out += ((ll)dp[i] * (ll)x)/r;
			}
			cout << fixed << setprecision(8) << out << endl;
		}
		else {
			double out = 0;
			rep1(i, m) {
				int x = i - k;
				if (x <= 0)x = 1;
				out += x/(double)m;
			}
			cout << fixed << setprecision(8) << out << endl;
		}
	}
	return 0;
}
