#include <iostream>
#include <cstdio>
#include <cmath>

using namespace std;

int n, m, k, x;
double ans;

void dfs(int node, int sum) {
    if (node == n) {
        if (sum-k < 1) sum = 1;
        else sum -= k;
        ans += (double)sum / x;
        return;
    }
    for (int i = 1; i < m+1; i++) {
        dfs(node+1, sum+i);
    }
    return;
}

int main(void){
    while (cin>>n>>m>>k && n) {
        ans = 0;
        x = pow(m,n);
        dfs(0, 0);
        printf("%.12lf\n",ans);
    }
}