#include <iostream>
#include <cstdio>
#include <math.h>
using namespace std;
double res,k,n;

void check(double a,double m,double x){
	if(a == 0){
		if(x-k < 1){
			x = 1;
			res += (1/pow(m,n)) * x;
		}
		else res += (1/pow(m,n)) * (x-k);
	}
	else{
		for(int i = 1;i <= m;i++){
			check(a-1,m,x+i);
		}
	}
}

int main(){
	double m;
	while(1){
		res = 0;
		cin >> n >> m >> k;
		if(n == 0)break;
		check(n,m,0);
		printf("%.10f\n",res);
	}
	return 0;
}