using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (f, n, k) = (c[0], c[1], c[2]);
        var ans = 0.0;
        for (var t = 1; t <= f; ++t) for (var i = 0; i < k; ++i) for (var j = Math.Max(1, k - i); i + j <= n; ++j)
        {
            // tより大きい目がi個、tがj個、tより小さい目がn-i-j個出る確率
            var p = 1.0;
            for (var x = 0; x < i; ++x) p *= (double)(f - t) / f * (n - x) / (x + 1);
            for (var x = 0; x < j; ++x) p *= 1.0 / f * (n - i - x) / (x + 1);
            for (var x = 0; x + i + j < n; ++x) p *= (double)(t - 1) / f;
            ans += p * t;
        }
        WriteLine(ans);
    }
}