#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=(n);i<(int) N;i++)
#define p(s) cout<<(s)<<endl
using namespace std;

int A[4];
int B[4];
int main() {
	int n;
	cin>>n;
	REP(i,0,n) cin>>A[i];
	REP(i,0,n) cin>>B[i];
	vector<int> vt(n);
	REP(i,0,n) vt[i]=i;
	int ok = 0;
	int cnt = 0;
	do{
		int win = 0;
		REP(i,0,n)
		{
			if (A[vt[i]] > B[i]) win++;
			else win--;
		}
		if (win > 0) ok++;
		cnt++;
	} while (next_permutation(vt.begin(), vt.end()));
	printf("%.3lf",(double)ok/cnt);
	return 0;
}