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;
		C[0][0] = 1;
		for (int i = 1; i < 200; ++i) {
			for (int j = 0; j <= i; ++j) {
				C[i][j] = C[i - 1][j] + (j > 0 ? C[i - 1][j - 1] : 0);
			}
		}
		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 p = 1.0 / F;
		double ans = 0;
		// 100
		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);
	}

	double[][][] memo = new double[200][200][200];
	{
		for (int i = 0; i < memo.length; ++i)
			for (int j = 0; j < memo[i].length; ++j)
				for (int k = 0; k < memo[i][j].length; ++k)
					memo[i][j][k] = -1;

	}

	double f(int i, int j, int k, double F) {
		if (i < 0 || j < 0 || k < 0)
			return 0;
		if (j == 0 && k == 0)
			return 1;
		if (j == 1) {
			if (k == 1) {
				return 1.0 / F * i;
			} else {
				return 0;
			}
		}
		if (memo[i][j][k] >= 0)
			return memo[i][j][k];
		return memo[i][j][k] = 1.0 / F * (f(i, j - 1, k, F) * k + f(i, j - 1, k - 1, F) * (i - (k - 1)));
	}

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

}