#include<bits/stdc++.h>
#define INF 1e12

using namespace std;
typedef long long int ll;

int main()
{
   int N; cin >> N;
   vector<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.begin(),A.end());
   sort(B.begin(),B.end());
   long double sum = 0;
   long double S = 0;
   do
   {
       do
       {
           S++;
           int p = 0;
           for(int i = 0; i < N; i++)
           {
               if(A[i] > B[i]) p++;
               if(A[i] < B[i]) p--;
           }
           if(p > 0) sum++;
       }while(next_permutation(B.begin(),B.end()));
   }while(next_permutation(A.begin(),A.end()));
   cout << fixed << setprecision(10) << sum / S << endl;
}