import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		new Main().run();
	}

	void run() {
		Scanner sc = new Scanner(System.in);
		long[][] C = new long[200][200];
		double[] fac = new double[170];
		fac[0] = 1;
		for (int i = 1; i < fac.length; ++i)
			fac[i] = fac[i - 1] * i;
		double F = sc.nextInt();
		int N = sc.nextInt();
		int K = sc.nextInt();
		double ans = 0;
		for (int val = 1; val <= F; ++val) {
			for (int u = 0; u <= K - 1; ++u) {
				for (int v = K - u; u + v <= N; ++v) {
					ans += val * fac[N] / fac[u] / fac[v] / fac[N - u - v] * Math.pow((F - val) / F, u)
							* Math.pow(1 / F, v) * Math.pow((val - 1) / F, N - (u + v));
				}
			}
		}
		System.out.println(ans);
	}

	void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}

}