#include <algorithm>
#include<bits/stdc++.h>

using namespace std;

using db = long double;

const int maxn = 510;

void solve() {
    int n, a, b;
    cin >> n >> a >> b;
    vector<int> vec(n + 10);
    for (int i = 0; i < n; i++) cin >> vec[i];
    vector<vector<db>> dp(n + 10, vector<db>(b + 10, 0));
    auto ndp = dp;
    dp[0][0] = 1;
    for (int i = 0; i < n; i++) {
        for (auto &v: ndp) fill(begin(v), end(v), 0);
        for (int x = 0; x <= i; x++) {
            for (int y = 0; y <= b; y++) {
                ndp[x][y] += dp[x][y];
            }
            for (int y = 0; y <= b - vec[i]; y++) {
                ndp[x + 1][y + vec[i]] += dp[x][y] * (x + 1) / (n - x);
            }
        }
        dp = ndp;
    }
    db ans = 0;
    for (int i = 0; i < n; i++) {
        ndp = dp;
        for (int x = 0; x < n; x++) {
            for (int y = 0; y <= 500; y++) {

                if (x >= 1 && y >= vec[i]) {
                    ndp[x][y] -= ndp[x - 1][y - vec[i]] * (x) / (n - x + 1);
                }
            }
        }
        db temp = 0;
        for (int x = 0; x < n; x++) {
            db t1 = 0;
            for (int y = max(0, a - vec[i] + 1); y <= min(a, b - vec[i]); y++) {
                t1 += ndp[x][y];
            }
            temp += t1 / (n - x + 1e-9);
        }
        ans += temp;
    }
    cout << fixed << setprecision(30) << (long double) ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}