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

int main(){
  int n; cin >> n;
  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, a+n); sort(b, b+n);

  int win=0, cnt=0;
  do{
    do{
      int tmpWin=0;
      for(int i=0; i<n; i++) {
        if(a[i]>b[i]) tmpWin++;
      }
      if(tmpWin > n-tmpWin) win++;
      cnt++;
    }while(next_permutation(b, b+n));
  }while(next_permutation(a, a+n));
  
  printf("%lf\n", (win*1.0)/cnt);
  return 0;
}