#include <bits/stdc++.h>
#define perr(a...) fprintf(stderr, a)
#define dbg(a...) perr("\033[32;1m"), perr(a), perr("\033[0m")
template <class T, class U>
inline bool smin(T &x, const U &y) {
  return y < x ? x = y, 1 : 0;
}
template <class T, class U>
inline bool smax(T &x, const U &y) {
  return x < y ? x = y, 1 : 0;
}
 
using LL = long long;
using PII = std::pair<int, int>;
 
int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int n, a, b;
  std::cin >> n >> a >> b;
  std::vector<std::vector<double>> f(1, std::vector<double>(b + 1)), g;
  f[0][0] = 1;
  std::vector<int> v(n);
  for (auto &x : v) {
    std::cin >> x;
    f.emplace_back(b + 1);
    for (int i = f.size() - 1; i; i--) {
      for (int j = b; j >= x; j--) {
        f[i][j] += f[i - 1][j - x] / (n - i + 1) * i;
      }
    }
  }
  double ans = 0;
  for (auto x : v) {
    g = f;
    for (int i = 1; i <= n; i++)
      for (int j = x; j <= b; j++) {
        g[i][j] -= g[i - 1][j - x] / (n - i + 1) * i;
      }
    for (int i = 0; i < n; i++) {
      for (int j = std::max(a + 1, x); j - x <= a && j <= b; j++) {
        ans += g[i][j - x] / (n - i);
      }
    }
  }
  printf("%.10f\n", ans);
  return 0;
}