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

int n, m, k;

int dfs(int t, int sum) {
    if (t == n) {
        sum = max(1, sum-k);
        return sum;
    }
    int res = 0;
    for (int i=1; i<=m; ++i) {
        res += dfs(t+1, sum+i);
    }
    return res;
}

int main() {
    while (cin >> n >> m >> k) {
        if (!n) break;
        printf("%.8f\n", dfs(0, 0) / (double)pow(m, n));
    }
    return 0;
}
