Go: package main

import (
	"fmt"
	"math"
)

func main(){
	var n, m, k int
	for {
		fmt.Scan(&n, &m, &k)
		if n == 0 && m == 0 && k == 0{
			break
		}

		dp := make([][]int, n+1)
		for i:= 0; i < n+1; i++{
			dp[i] = make([]int, m*n + 1)
		}

		for i := 1; i <=m ; i++{
			dp[1][i] = 1
		}

		for i:= 1; i < n; i++{
			for j := 0; j <= i * m; j++{
				for k := 1; k <= m; k++{
					dp[i+1][j+k] += dp[i][j]
				}
			}
		}

		count := 0.0
		div := math.Pow(float64(m), float64(n))
		for i := 0; i <= n * m; i++{
			bill := 0.0
			if i <= k{
				bill = 1.0
			} else {
				bill = float64(i - k)
			}
			count += bill * float64(dp[n][i]) / div
		}
		fmt.Printf("%.010f\n", count)
	}
}

C++: #include <iostream>
#include <cmath>

#define N 100000000

using namespace std;

main(){
  int n, m, k;
  while(1){
    cin >> n >> m >> k;
    if(n==0 && m==0 && k==0) break;

    int data[N];
    for(int i=0;i<=n*m;i++) data[i]=0;
    int num[15];
    for(int i=1;i<=n;i++) num[i]=1;
    bool end=false;
    for(;;){
      int sum=0;
      for(int i=1;i<=n;i++){
	sum+=num[i];
      }
      data[sum]++;
      if(num[n]==m){
	num[n]=0;
	for(int t=n-1;;){
	  if(t<=0){
	    end=true;
	    break;
	  }
	  if(num[t]<m){
	    num[t]++;
	    break;
	  }else{
	    num[t]=1;
	    t--;
	  }
	}
	if(end) break;
      }
      num[n]++;
    }
    double ans=0;
    for(int i=1;i<=k;i++){
      ans+=(double)data[i]/pow((double)m, (double)n);
    }
    for(int i=k+1, j=1;i<=n*m;i++, j++){
      ans+=(double)data[i]*j/pow((double)m, (double)n);
    }
    printf("%.10f\n", ans);
  }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <list>
#include <complex>
#include <algorithm>
#include <set>
#include <map>
#include <queue>
#include <string>
#include <cstring>
#include <stack>
#include <cmath>
#include <iomanip>
#include <sstream>
#include <fstream>
#include <cassert>
#include <numeric>
using namespace std;
typedef long long ll;
typedef pair<int,int> PI;
#define EPS (1e-6)
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define REP(i, n) rep (i, n)
#define F first
#define S second
#define mp(a,b) make_pair(a,b)
#define pb(a) push_back(a)
#define min3(a,b,c) min((a),min((b),(c)))
#define min4(a,b,c,d) min((a),min3((b),(c),(d)))
#define SZ(a) (int)((a).size())
#define ALL(a) a.begin(),a.end()
#define FLL(a,b) memset((a),b,sizeof(a))
#define CLR(a) memset((a),0,sizeof(a))
#define FOR(it,a) for(__typeof(a.begin())it=a.begin();it!=a.end();++it)
template<typename T,typename U> ostream& operator<< (ostream& out, const pair<T,U>& val){return out << "(" << val.F << ", " << val.S << ")";}
template<class T> ostream& operator<< (ostream& out, const vector<T>& val){out << "{";rep(i,SZ(val)) out << (i?", ":"") << val[i];return out << "}";}
typedef double FP;
typedef complex<FP> pt;
typedef pt P;
typedef pair<pt,pt> line;
FP dot(P a,P b){return real(conj(a)*b);}
FP crs(P a,P b){return imag(conj(a)*b);}
P ortho(P a){return conj(P(imag(a),real(a)));}
P ortho(line a){return ortho(a.S-a.F);}
P crspt(P a,P b,P c,P d){b-=a,d-=c;return a+b*crs(d,c-a)/crs(d,b);}
P crspt(line a,line b){return crspt(a.F,a.S,b.F,b.S);}
bool onl(P a1,P a2,P b){return abs(b-a1)+abs(b-a2)<abs(a1-a2)+EPS;}
bool onl(line a,P b){return onl(a.F,a.S,b);}
bool iscrs(line a,line b){P c=crspt(a,b);return onl(a,c)&&onl(b,c);}
void pkuassert(bool t){t=1/t;};
int dx[]={0,1,0,-1,1,1,-1,-1};
int dy[]={1,0,-1,0,-1,1,1,-1};
enum{TOP,BTM,LFT,RGT,FRT,BCK};
int dxdy2ce[]={RGT,FRT,LFT,BCK};
template<class T> T shift(T a,int b,int c,int d,int e){
 __typeof(a[0])t=a[b];a[b]=a[c];a[c]=a[d];a[d]=a[e];a[e]=t;
 return a;}
template<class T> T rgt(T a){return shift(a,TOP,LFT,BTM,RGT);}
template<class T> T lft(T a){return shift(a,TOP,RGT,BTM,LFT);}
template<class T> T frt(T a){return shift(a,TOP,BCK,BTM,FRT);}
template<class T> T bck(T a){return shift(a,TOP,FRT,BTM,BCK);}
line mkl(P a,P v){return line(a,a+v);}
FP lpdist(line a,P b){return abs(b-crspt(a,mkl(b,ortho(a))));}
FP spdist(line a,P b){
  P c(crspt(a,mkl(b,ortho(a))));
  return onl(a,c)?abs(b-c):min(abs(a.F-b),abs(a.S-b));
}
FP ssdist(line a,line b){
 return
  iscrs(a,b)?0.:
   min4(spdist(a,b.F),spdist(a,b.S),
        spdist(b,a.F),spdist(b,a.S));
}
namespace std{
  bool operator<(const P&a,const P&b){
    return mp(real(a),imag(a))<mp(real(b),imag(b));
  }
}

int n,m,k;
ll allsum;
void dfs(int sum,int depth){
  if(depth==n){
    allsum+=max(sum-k,1);
    return;
  }
  for(int i=1;i<=m;++i)
    dfs(sum+i,depth+1);
}

void solve(){
  allsum=0;
  dfs(0,0);
  printf("%.8f\n",allsum/pow(m,n));
}

int main(int argc, char *argv[])
{
  while(cin >> n >> m >> k && n) solve();
  return 0;
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<cstdio>
#include<sstream>
#include<algorithm>
#include<cmath>
#include<map>
#include<functional>
#include<queue>
#include<stack>
#include<set>
using namespace std;
#define SZ(n)  (int)n.size()
#define dump(x) cerr<<#x<<" = "<<(x)<<endl;
#define debug(x)cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#define MP make_pair
#define PB push_back
const int INF=1<<28;
	int n,m,k;
	int p[300000];
	void dfs(int now,int sum){
		if(now==n)p[sum]++;
		if(now==n)return ;
		for(int i=1;i<=m;i++)dfs(now+1,sum+i);
	}
	
	int main(){
	while(cin>>n>>m>>k,n+m+k){
	dfs(0,0);
	double ans=0.0;
	int kaku=pow(m,n);
	for(int i=1;i<=m*n;i++){
		double a=(double)p[i]/double(kaku);
		double b=max(double(i-k),1.0);
		ans+= a*b;
	}
	printf("%.10lf",ans);
	fill(p,p+300000,0);
	}
	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define REP(i, n) FOR(i, 0, n)
#define RFOR(i, a, b) for(int i=(a);i>=(b);i--)
#define RREP(i, n) RFOR(i, n, 0)
#define MFOR(i, m) for(auto i=(m).begin();i!=(m).end();i++)
#define ALL(a) (a).begin(), (a).end()
#define SZ(x) ((int)(x).size())

typedef long long int ll;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vll;
typedef vector<vll> vvll;

const double eps = 1e-10;
const int MOD = 1000000007;
const int INF = 1000000000;
const ll LINF = 1ll<<50;

template<typename T>
void printv(vector<T> const& s) {
  REP(i, SZ(s)) {
    cout << s[i];
    if(i == SZ(s)-1) {
      cout << endl;
    } else {
      cout << " ";
    }
  }
}

int po(int m, int n) {
  int res = 1;
  for(int i=0;i<n;++i) {
    res *= m;
  }
  return res;
}

ll sum(int cb, int m, int n, int k, vector<int> dice) {
  ll res = 0;
  if(k == n) {
    for(int i=0;i<n;++i) {
      res += dice[i];
    }
    res = max(1ll, res - cb);    
  } else {
    dice.push_back(0);
    int last = SZ(dice)-1;
    for(int i=1;i<=m;++i) {
      dice[last] = i;
      res += sum(cb, m, n, k+1, dice);
    }
  }
  return res;
}

int main () {
  cin.tie(0);
  cout << fixed << setprecision(10);

  while(1) {
    int n, m, k; cin >> n >> m >> k;
    if(n == 0 && m == 0 && k == 0) break;
    vi dice;
    cout << sum(k, m, n, 0, dice) / (double)po(m, n) << endl;
  }
}