#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#include "bits/stdc++.h"
#define REP(i,a,b) for(int i=a;i<b;++i)
#define rep(i,n) REP(i,0,n)
#define ll long long
#define ull unsigned ll
typedef long double ld;
#define ALL(a) begin(a),end(a)
#define ifnot(a) if(not a)
#define dump(x)  cerr << #x << " = " << (x) << endl
using namespace std;

// #define int ll
#ifdef _MSC_VER
const bool test = true;
#else 
const bool test = false;
#endif

int dx[] = { 0,1,0,-1 };
int dy[] = { 1,0,-1,0 };
#define INF (1 << 28)
ull mod = (int)1e9 + 7;
//.....................
#define MAX (int)1e6 + 5

int n, m, k;

template<class T>
T pow(T x, T n) {
	T res = 1;
	while (n > 0) {
		if (n & 1) res = res * x;
		x = x * x;
		n >>= 1;
	}
	return res;
}

ll dfs(int now_v,int cnt) {
	if (cnt == n) return max(now_v - k, 1);
	ll res = 0;
	REP(i, 1, m + 1) res += dfs(now_v + i, cnt + 1);
	return res;
}

signed main() {
	cout << setprecision(20) << fixed;
	while (cin >> n >> m >> k) {
		if (n == 0) break;
		cout << (double)dfs(0, 0) / pow(m, n) << endl;
	}
	return 0;
}