#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;

int main () {
  int n; cin >> n;
  vector<int> a(n);
  vector<int> 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());
  vector<vector<int> > vec;
  do {
    vec.push_back(b);
  } while(next_permutation(b.begin(), b.end()));
  int res = 0;
  do {
    for(int i=0; i<vec.size(); i++) {
      int sa = 0, sb = 0;
      for(int j=0; j<n; j++) {
        if(a[j] > vec[i][j]) sa++;
        else sb++;
      }
      if(sa > sb) res++;
    }
  } while(next_permutation(a.begin(), a.end()));
  cout << (double)res/(vec.size()*vec.size()) << endl;
}