#include <bits/stdc++.h>
#define int long long
//#define USE_FREOPEN
//#define MUL_TEST
#define FILENAME ""
using namespace std;

void solve() {
	int F, N, K;
	cin >> F >> N >> K;
	double ans = 0;
	for (int x = 1; x <= F; x++) {
		double p1 = 1.0 * (F - x) / F;
		double p2 = 1.0 / F;
		double p3 = 1.0 - p1 - p2;
		
		double sump = 0;
		for (int i = 0; i < K; i++) {
			for (int j = K - i; j <= N - i; j++) {
				int k = N - i - j;
				double p = 1;
				for (int l = 1; l <= i; l++) p *= p1;
				for (int l = 1; l <= j; l++) p *= p2;
				for (int l = 1; l <= k; l++) p *= p3;
				for (int l = 1; l <= N; l++) p *= l;
				for (int l = 1; l <= i; l++) p /= l;
				for (int l = 1; l <= j; l++) p /= l;
				for (int l = 1; l <= k; l++) p /= l;
				sump += p;
			}
		}
		ans += sump * x;
	}
	printf("%.15lf\n", ans);
}

signed main() {
//	ios::sync_with_stdio(false);
//	cin.tie(nullptr); cout.tie(nullptr);

	#ifdef USE_FREOPEN
		freopen(FILENAME ".in", "r", stdin);
		freopen(FILENAME ".out", "w", stdout);
	#endif
	int _ = 1;
	#ifdef MUL_TEST
		cin >> _;
	#endif
	while (_--)
		solve();
	_^=_;
	return 0^_^0;
}