#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
#define fi first
#define se second
#define repl(i,a,b) for(ll i=(ll)(a);i<(ll)(b);i++)
#define rep(i,n) repl(i,0,n)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<x<<endl
#define mmax(x,y) (x>y?x:y)
#define mmin(x,y) (x<y?x:y)
#define maxch(x,y) x=mmax(x,y)
#define minch(x,y) x=mmin(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt __builtin_popcountll
#define INF 1e16
#define mod 1000000007
int main() {
	int N;
	cin >> N;
	vector<int> A(N);
	vector<int> B(N);
	for (int i = 0; i < N; i++)
	{
		cin >> A[i];
	}
	for (int i = 0; i < N; i++)
	{
		cin >> B[i];
	}

	vector<int> NA(N), NB(N);
	for (int i = 0; i < N; i++)
	{
		NA[i] = NB[i] = i;
	}
	int ok = 0;
	int count = 0;
	do{
		do{
			int win = 0;
			for (int i = 0; i < N; i++)
			{
				if (A[NA[i]] > B[NB[i]]) win++;
				else win--;
			}
			if (win > 0) ok++;
			count++;
		} while (next_permutation(NA.begin(), NA.end()));
	} while (next_permutation(NB.begin(), NB.end()));

	printf("%.14f\n", (double)ok / count);
}