#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <numeric>
#include <string>
#include <string.h>
#include <map>
#include <set>
#include <functional>
#include <complex>
#include <stack>
#include <tuple>
#include <array>
using namespace std;
#define rep(i,n) for (int i=0; i < (n); i++)


typedef long long int ll;
typedef double D;      // ??§?¨?????????????double???long double?????????
typedef complex<D> P;  // Point
typedef pair<P, P> L;  // Line
typedef vector<P> VP;


const int INF = (1<<30) - 1;
const D EPS = 1e-9;

#define X real()
#define Y imag()
#define LE(n,m) ((n) < (m) + EPS)
#define GE(n,m) ((n) + EPS > (m))
#define EQ(n,m) (abs((n)-(m)) < EPS)

int N, M, K;

int dfs(int cur, vector<int> nums){
    if(cur == 0){
        int s = 0;
        for(int i=0; i<nums.size(); i++)
            s += nums[i];
        return s-K > 0 ? s-K: 1;
    }
    
    int ans = 0;
    nums.push_back(-1); //dummy;
    for(int i=1; i<=M; i++){
        nums[nums.size()-1] = i;
        ans += dfs(cur-1, nums);
    }
    return ans;
}

void solve(){
    double d = dfs(N, {});
    for(int i=0; i<N; i++)
        d /= M;
    printf("%.7lf\n", d);
}

//g++ -std=c++0x -msse4.2 -O3
//#include <bits/stdc++.h>
int main(){
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.precision(16);
    
    while(cin>>N>>M>>K, N|M|K)
        solve();
    
    return 0;
}