#include <bits/stdc++.h>
#define FOR(I,X,Y) for(int I=X;I<Y;I++)
#define REP(I,X,Y) for(int I=Y-1;I>=X;I--)
#define INF 1000000007
using namespace std;

int main(){
  int N;
  double all = 0,won = 0;
  cin >> N;
  vector<int> A(N),B(N);
  FOR(i,0,N)cin >> A[i];
  FOR(i,0,N)cin >> B[i];
  sort(A.begin(),A.end());
  sort(B.begin(),B.end());
  do{
    do{
      all++;
      int k = 0;
      FOR(i,0,N)if(A[i] > B[i])k++;
      if(k > N-k)won++;
    }while(next_permutation(A.begin(),A.end()));
  }while(next_permutation(B.begin(),B.end()));
  cout << fixed << won/all << endl;
}