#include <bits/stdc++.h>
using namespace std;

int main() {
  int n, a[4], b[4], x[] {0, 1, 2, 3}, an {};
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
  }
  for (int i = 0; i < n; ++i) cin >> b[i];
  do {
    int w {};
    for (int i = 0; i < n; ++i) {
      if (b[i] < a[x[i]]) ++w;
    }
    if (n < w * 2) ++an;
  }while (next_permutation(x, x + n));
  int div {1};
  for (int i = 1; i <= n; ++i) div *= i;
  cout << an / (double)div << '\n';
}