#include <bits/stdc++.h>

using namespace std;

int main() {
  auto start = clock();

  int N, A[20], B[20];
  double X, Y;
  cin >> N >> X >> Y;
  for(int i = 0; i < N; i++) cin >> A[i];
  for(int i = 0; i < N; i++) cin >> B[i];
  sort(A, A + N);
  sort(B, B + N);

  random_device rnd;
  mt19937 mt(rnd());
  uniform_real_distribution<> gen(0, 1);
  int win = 0, times = 0;

  while(clock() - start < 2.9 * CLOCKS_PER_SEC) {
    ++times;
    bool used1[20] = {}, used2[20] = {};
    int latte = 0, malta = 0;
    for(int i = 0; i < N; i++) {
      int p, q;

      auto x = gen(mt);
      if(x <= X) {
        for(int j = 0; j < N; j++) {
          if(used1[j]) continue;
          used1[j] = true;
          p = A[j];
          break;
        }
      } else {
        int y = (int) (gen(mt) * (N - i - 1)) + (i + 1 != N);
        for(int j = 0; j < N; j++) {
          if(used1[j]) continue;
          if(y == 0) {
            used1[j] = true;
            p = A[j];
            break;
          }
          --y;
        }
      }

      x = gen(mt);
      if(x <= Y) {
        for(int j = 0; j < N; j++) {
          if(used2[j]) continue;
          used2[j] = true;
          q = B[j];
          break;
        }
      } else {
        int y = (int) (gen(mt) * (N - i - 1)) + (i + 1 != N);
        for(int j = 0; j < N; j++) {
          if(used2[j]) continue;
          if(y == 0) {
            used2[j] = true;
            q = B[j];
            break;
          }
          --y;
        }
      }
      if(p > q) latte += p + q;
      if(q > p) malta += p + q;
    }
    if(latte > malta) {
      ++win;
    }
  }
  cout << fixed << setprecision(5) << 1.0 * win / times << endl;
}