#include<bits/stdc++.h>

using namespace std;

using db = long double;

const int maxn = 505;
db dp[maxn][maxn], ndp[maxn][maxn];
int vec[maxn];

void solve() {
    int n, a, b;
    cin >> n >> a >> b;
    for (int i = 1; i <= n; i++) cin >> vec[i];

    dp[0][0] = 1;

    for (int i = 1; i <= n; i++) {
        memset(ndp, 0, sizeof(ndp));
        for (int x = 0; x <= i && (x <= n - 1); x++) {
            for (int y = 0; y <= b; y++) {
                ndp[x][y] += dp[x][y];
                if (y + vec[i] <= b) ndp[x + 1][y + vec[i]] += dp[x][y] * (x + 1) / (n - x);
            }
        }
        memcpy(dp, ndp, sizeof(ndp));
    }

    db ans = 0;
    for (int i = 1; i <= n; i++) {
        memcpy(ndp, dp, sizeof(dp));
        for (int x = 0; x <= n - 1; x++) {
            for (int y = 0; y <= b; y++) {
                ndp[x + 1][y + vec[i]] -= ndp[x][y] * (x + 1) / (n - x + 1e-18);
            }
        }
        for (int x = 0; x <= n - 1; x++) {
            for (int y = 0; y <= a; y++) {
                if (y + vec[i] > a and y + vec[i] <= b) {
                    ans += ndp[x][y] / (n - x);
                }
            }
        }
    }
    cout << fixed << setprecision(20) << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    solve();

    return 0;
}