//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <climits>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>
#include <random>
#include <complex>
#include <regex>

using namespace std;

#define SHOW_VECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOW_MAP(v){std::cerr << #v << endl; for(const auto& xxx: v){std::cerr << xxx.first << " " << xxx.second << "\n";}}

long long dfs(long long N, long long M, long long K, long long d, long long sum) {
    if (d == N) return max(1LL, sum - K);
    long long ret = 0;
    for (long long i = 1; i <= M; i++) {
        ret += dfs(N, M, K, d + 1, sum + i);
    }
    return ret;
}

int main() {

    while (true) {

        long long N, M, K;
        cin >> N >> M >> K;

        if (!(N | M | K)) break;

        long long nomi = dfs(N, M, K, 0, 0);
        double deno = 1;
        for (int i = 0; i < N; i++) deno *= M;

        cout << fixed << setprecision(10) << (double) nomi / deno << endl;

    }

    return 0;
}




























































