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

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<int> a(n), b(n);
  for(int i=0;i<n;i++)
    cin >> a[i];
  for(int i=0;i<n;i++)
    cin >> b[i];
  sort(a.begin(), a.end());
  sort(b.begin(), b.end());

  int sum = 0, win = 0;
  do {
    do {
      int w = 0;
      sum++;
      for(int i=0;i<n;i++) {
        if(a[i] > b[i])
          w++;
        else if(a[i] < b[i])
          w--;
      }
      if(w > 0)
        win++;
    } while( next_permutation(b.begin(), b.end()));
  } while( next_permutation(a.begin(), a.end()));

  printf("%.8f\n", (double) win / sum);
}