import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.util.Scanner;

public class C {
    public static void main(String[] args) {
        int n = 0;
        int m = 0;
        int k = 0;

        double[][] probDistribution = new double[2][9];

        try (Scanner sc = new Scanner(System.in)) {
            n = sc.nextInt();
            m = sc.nextInt();
            k = sc.nextInt();
        }

        probDistribution[1][0] = 1;

        for (int i = 1; i <= k; i++) {
            int last = Math.min(m * n, i) - 1;
            probDistribution[1][last] = 1;

            for (int j = 0; j < last; j++) {
                if (j == 0) {
                    probDistribution[1][j] /= (m * n);
                } else {
                    double one = probDistribution[0][j - 1] * (m * n - j) / (m * n);
                    double two = probDistribution[0][j] * (j + 1) / (m * n);

                    probDistribution[1][j] = one + two;

                }
                probDistribution[1][last] -= probDistribution[1][j];
            }

            for (int j = 0; j < i; j++) {
                probDistribution[0][j] = probDistribution[1][j];
            }
        }

        double expectedValue = 0;

        int maxTarget = Math.min(k, m * n);

        for (int i = 0; i < maxTarget; i++) {
            double v = (i + 1d) * probDistribution[0][i];
            expectedValue += v;
        }

        System.out.println(printDoubleJava(expectedValue));
    }

    public static String printDoubleJava(double d) {
        DecimalFormat df = new DecimalFormat("0.000000000000");
        df.setRoundingMode(RoundingMode.HALF_UP);

        return df.format(d);
    }
}