#include <iostream>
#include <cstdio>
using namespace std;

int main(){
	int n, m, k;
	while( cin >> n >> m >> k , n || m || k ){
		int s = n * m;
		double dp[2][s+5];
		for(int i=0 ; i < s+5 ; i++ ){
			dp[0][i] = dp[1][i] = 0.0;
		}
		dp[0][0] = 1.0;
		for(int i = 0 ; i < n ; i++ ){
			for(int j = i ; j < s+5 ; j++ ){
				for(int k = 1 ; k < m+1 ; k++ ){
					if( s + 5 < j + k ) break;
					dp[1][j+k] += dp[0][j] * (1.0 / m);
				}
			}
			for(int j = i ; j < s+5 ; j++ ){
				dp[0][j] = dp[1][j];
				dp[1][j] = 0;
			}
		}
		double ans = 0.0;
		for(int i = 1 ; i < s+5 ; i++ ){
			if( i - k <= 1 ){
				ans += dp[0][i];
			}else{
				ans += dp[0][i] * (i - k);
			}
		}
		printf("%.8f\n", ans);
	}
}