#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int n;
vector<int> a,b;
void input(){
  cin >> n;
  for(int i=0;i<n;++i){
    int x; cin >> x;
    a.push_back(x);
  }
  for(int i=0;i<n;++i){
    int x; cin >> x;
    b.push_back(x);
  }
}

void solve(){
  int awin = 0;
  int battle = 0;
  do{
    sort(b.begin(),b.end());
    do{
      int acnt = 0,bcnt = 0;
      for(int i=0;i<n;++i){
	if(a[i] > b[i]) ++acnt;
      }
      if(acnt>n/2) ++awin;
      ++battle;
    }while(next_permutation(b.begin(),b.end()));
  }while(next_permutation(a.begin(),a.end()));
  cout << 1.0 * awin / battle << endl;
}

int main(){
  input();
  solve();
  return 0;
}