#define _USE_MATH_DEFINES
#include <iostream>
#include <iomanip>
#include <utility>
#include <algorithm>
#include <vector>
#include <cmath>
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
#define Rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define rev(i,n) for(int i=n-1;i>=0;i--)
#define vi vector<int>
#define vvi vector<vi>
#define pb push_back
#define pi pair<int,int>
#define vp vector<pair<int,int>>
#define mp make_pair
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
#define MEMSET(a) memset(a,0,sizeof(a))
#define inf (1ll<<60)
#define Yes(f) cout<<(f?"Yes":"No")<<endl
#define yes(f) cout<<(f?"yes":"no")<<endl
#define YES(f) cout<<(f?"YES":"NO")<<endl

using namespace std;

const int mod=1e9+7;

void run();

void init() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout<<fixed<<setprecision(12);
}

signed main(){
    init();
    run();
    return 0;
}

int N;
int M;
int K;
int t;

// n maisu k menowa
void rec(int n,int k){
  if(n==N){
    t+=(k-K>0)?k-K:1;
    return;
  }
  REP(i,1,M){
    rec(n+1,k+i);
  }
}

void run(){
  while(cin>>N>>M>>K,N){
    t=0;
    rec(0,0);
    double ans=(double)t;
    double p=pow(M,N);
    cout<<ans/p<<endl;
  }
}

