#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;
int cnt;

void dfs(int i, int sm) {
    if (i == n) {
        cnt += max(1LL, 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 = 0;
        dfs(0, 0);
        printf("%.10f\n", cnt / pow(m, n));
    }
}