#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <set>
#include <unordered_set>
#include <cstring>
#include <queue>
#include <bitset>
#include <map>
#include <stack>

using namespace std;

long double dp[101][101];
int f,n,k;
long double C[101][101];

int main() 
{
	cin.tie(0);
    ios::sync_with_stdio(false);

	cin >> f >> n >> k;
	long double p = 1;
	p/=f;

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

	k = (n+1) - k;

	dp[0][0] = 1;

	for(int i=0;i<=n;i++)
	{
		for(int j=0;j<f;j++)
		{
			if(dp[i][j]==0) continue;
			//cout << i << ' ' << j << ' ' << dp[i][j] << '\n';
			dp[i][j+1] += dp[i][j];
			double P = 1;
			for(int a=i+1;a<=n;a++)
			{
				P*=p;
				long double value = P;
				value*=C[(n-i)][a-i];
				value*=dp[i][j];
				if(i<k && a>=k) value*=(j+1);
				dp[a][j+1] += value;
			}
		}
	}

	cout << fixed;
	cout.precision(16);

	cout << dp[n][f] << '\n';
    return 0;
}