#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
using Graph = vector<vector<ll>>;
ll mod = 998244353;
ll inva(ll N) {
    ll a = N, b = mod, c = 1, d = 0;
    while (b > 0) {
        ll t = a / b;
        a -= t * b;
        swap(a, b);
        c -= t * d;
        swap(c, d);

    }
    c %= mod;
    if (c < 0)c += mod;
    return c;

}//割り算時に使う逆元を求める.


int main() {
    double F, N, K;
    cin >> F >> N >> K;
    double an = 0;
    rep(i, round(F)) {
        double A = 0;
        double s = double(i) / F;
        double e = 1.0 / F;
        double b = 1.0 - e - s;
        rep(j, round(K))rep(k, round(N - K)+1) {
            double m = 1;
            rep(q, j)m *= b;
            rep(q, k)m *= s;
            rep(q, round(N) - j - k)m *= e;
            rep(q, round(N))m *= (q + 1);
            rep(q, j)m /= (q + 1);
            rep(q, round(N) - j - k)m /= (q + 1);
            rep(q, k)m /= (q + 1);
            A += m;
        }
        an += A * (i + 1);
    }
    cout << setprecision(16) << an << endl;
}