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 <iomanip>
#include <vector>
#include <algorithm>

using namespace std;

vector<int> buffer;

int dfs(int m, int sum, int rem){
        if(rem == 0){
                ++(buffer[sum]);
                return 1;
        }
        int retval = 0;
        for(int i = 1; i <= m; ++i){ retval += dfs(m, sum + i, rem - 1); }
        return retval;
}

int main(){
        cout << setprecision(10);
        while(true){
                int n, m, k;
                cin >> n >> m >> k;
                if(n == 0 && m == 0 && k == 0){ break; }
                buffer.resize(n * m + 1);
                fill(buffer.begin(), buffer.end(), 0);
                int num = dfs(m, 0, n);
                double answer = 0.0;
                for(int i = 0; i < buffer.size(); ++i){
                        if(i <= k){
                                answer += 1.0 * buffer[i] / num;
                        }else{
                                answer += (double)(i - k) * buffer[i] / num;
                        }
                }
                cout << answer << endl;
        }
        return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define int long long   // <-----!!!!!!!!!!!!!!!!!!!

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n)-1;i>=0;i--)
#define rrep2(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define all(a) (a).begin(),(a).end()

typedef long long ll;
typedef pair<int, int> P;
typedef tuple<int, int, int> TUPLE;
typedef vector<int> V;
typedef vector<V> VV;
typedef vector<VV> VVV;

int n, m, k;
V cnt;

void dfs(int i, int sm) {
    if (i == n) {
        cnt[max<int>(1, sm - k)]++;
        return;
    }

    rep2(d, 1, m + 1) dfs(i + 1, sm + d);
}

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    while (cin >> n >> m >> k, n) {
        cnt.clear();
        cnt.resize(n * m + 1, 0);
        dfs(0, 0);

        double ans = 0;
        rep(i, cnt.size()) {
            ans += i * cnt[i];
        }
        printf("%.10f\n", ans / pow(m, n));
    }
}

C++: #include <bits/stdc++.h>
using namespace std;

#define MAX 100000008
double dp[MAX][2];

int main() {
	int n,m,k;
	while(1){
		cin >> n >> m >> k;
		if(n==0) break;
		for(int i=0;i<n*m+5;i++) dp[i][0] = 0;
		for(int i=0;i<m;i++)
			dp[i][0]=1/(double)m;
		for(int i=1;i<n;i++)
		{
			for(int j=0;j<n*m;j++)
				dp[j][i%2]=0;
//			for(int j=i-1;j<m*(i-1);j++)
			for(int j=0;j<m*n;j++)
				for(int k=0;k<m;k++)
				{
					dp[j+k+1][i%2]+=dp[j][(i+1)%2]/m;
					//cout << dp[j+k+1][i%2] << endl;
				}
		}
		double ans=0;
		for(int i=0;i<n*m;i++)
		{
			if((i+1-k)<=0)
				ans+=1*dp[i][(n+1)%2];
			else
				ans+=(i+1-k)*dp[i][(n+1)%2];
		}
		cout << fixed << setprecision(10) << ans << endl;
	}
}

C++: #include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <cassert>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>
#include <list>
#include <iomanip>
#include <fstream>
#include <bitset>
   
using namespace std;
   
 
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
#define rforeach(it, c) for (__typeof__((c).rbegin()) it=(c).rbegin(); it != (c).rend(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define CL(arr, val) memset(arr, val, sizeof(arr))
#define COPY(dest, src) memcpy(dest, src, sizeof(dest))
#define ten(n) ((long long)(1e##n))
#define bin(n) (1LL << (n))
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define revrep(i, n) for (int i = (n); i >= 0; --i)
#define pb push_back

template <class T> void chmax(T& a, const T& b) { a = max(a, b); }
template <class T> void chmin(T& a, const T& b) { a = min(a, b); }

template <class T> void uniq(T& c) { sort(c.begin(), c.end()); c.erase(unique(c.begin(), c.end()), c.end()); }
 
template <class T> string to_s(const T& a) { ostringstream os; os << a; return os.str(); }
template <class T> T to_T(const string& s) { istringstream is(s); T res; is >> res; return res; }

template <typename T> void print_container(ostream& os, const T& c) { const char* _s = " "; if (!c.empty()) { __typeof__(c.begin()) last = --c.end(); foreach (it, c) { os << *it; if (it != last) cout << _s; } } }
template <typename T> ostream& operator<<(ostream& os, const vector<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const set<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const multiset<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const deque<T>& c) { print_container(os, c); return os; }
template <typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& c) { print_container(os, c); return os; }
template <typename T, typename U> ostream& operator<<(ostream& os, const pair<T, U>& p) { os << "( " << p.first << ", " << p.second << " )"; return os; }

template <class T> void print(T a, int n, const string& deli = " ", int br = 1) { for (int i = 0; i < n; ++i) { cout << a[i]; if (i + 1 != n) cout << deli; } while (br--) cout << endl; }
template <class T> void print2d(T a, int w, int h, int width = -1, int br = 1) { for (int i = 0; i < h; ++i) { for (int j = 0; j < w; ++j) {    if (width != -1) cout.width(width); cout << a[i][j] << ' '; } cout << endl; } while (br--) cout << endl; }

template <class T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
template <class T> void input(T* a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }

void fix_pre(int n) { cout.setf(ios::fixed, ios::floatfield); cout.precision(10); }
void fast_io() { cin.tie(0); ios::sync_with_stdio(false); }
#define trace(x) (cout << #x << ": " << (x) << endl)
 
bool in_rect(int x, int y, int w, int h) { return 0 <= x && x < w && 0 <= y && y < h; }
bool in_seg(int n, int l, int r) { return l <= n && n < r; } // n in [l, r)?

typedef long long ll;
typedef pair<int, int> pint;

// y(v): v>^<  y(^): ^>v<
const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };

const double PI = acos(-1.0);
#define mp make_pair



int main()
{
    int n, m, k;
    while (scanf("%d%d%d", &n, &m, &k), n)
    {
        const int s = n * m;
        double dp[40][ten(4) + 100];
        erep(i, n) erep(j, s)
            dp[i][j] = 0;

        dp[0][0] = 1;
        rep(i, n) erep(j, s)
        {
            double p = dp[i][j] / m;
            for (int nj = j + 1, u = min(j + m, s); nj <= u; ++nj)
                dp[i + 1][nj] += p;
        }
        
        double res = 0;
        erep(j, s)
            res += max(1, j - k) * dp[n][j];
        printf("%.8f\n", res);
    }
}