#include <iostream>
#include <vector>
#include <algorithm>    // std::next_permutation, std::sort
using namespace std;
int main(int argc, char* argv[])
{
	int N;
	cin>>N;
	vector<int> A(N),B(N);
	int i,j;
	for (i=0;i<N;i++){
		cin>>A[i];
	}
	for (i=0;i<N;i++){
		cin>>B[i];
	}
	sort(A.begin(),A.end());
	vector<vector<int>> AList,BList;
	do{
		vector<int> A1;
		for (i=0;i<N;i++){
			A1.push_back(A[i]);
		}
		AList.push_back(A1);
	}while(next_permutation(A.begin(),A.end()));
	sort(B.begin(),B.end());
	do{
		vector<int> B1;	
		for (i=0;i<N;i++){
			B1.push_back(B[i]);
		}
		BList.push_back(B1);
	}while(next_permutation(B.begin(),B.end()));
	int AWin=0;
	int BWin=0;
	for (i=0;i<AList.size();i++){
		vector<int> AVal=AList[i];
		vector<int>::iterator ait;
		for (j=0;j<BList.size();j++){
			vector<int> BVal=BList[j];
			vector<int>::iterator bit;
			int aWin=0;
			int bWin=0;
			for (ait=AVal.begin(),bit=BVal.begin();ait!=AVal.end(),bit!=BVal.end();ait++,bit++){
				if ((*ait)>(*bit)){
					aWin++;
				}else if ((*ait)<<(*bit)){
					bWin++;
				}
			}
			if (aWin>bWin){
				AWin++;
			}else if (aWin<bWin){
				BWin++;
			}
		}
	}
	double ans=(double)AWin/(AList.size()*BList.size());
	cout<<ans<<endl;
	return 0;
}