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

int main() {
  int N;
  cin >> N;
  vector<int> A(N), B(N), C(N);
  for(int i=0; i<N; i++) cin >> A[i];
  for(int i=0; i<N; i++) cin >> B[i];
  for(int i=0; i<N; i++) C[i] = i;
  int match = 0, res = 0;
  do {
    int sa = 0, sb = 0;
    for(int i=0; i<N; i++) {
      if(A[i] > B[C[i]]) sa++;
      else sb++;
    }
    if(sa > sb) res++;
    match++;
  } while(next_permutation(C.begin(), C.end()));
  cout << (double)res/match << endl;
}