#include "bits/stdc++.h"
using namespace std;
#define ll long long int
#define rep(i,n) for( int i = 0; i < n; i++ )
#define rrep(i,n) for( int i = n; i >= 0; i-- )
#define REP(i,s,t) for( int i = s; i <= t; i++ )
#define RREP(i,s,t) for( int i = s; i >= t; i-- )
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define INF 2000000000
#define mod 1000000007
#define INF2 1000000000000000000


int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N; cin >> N;
	int A[N], B[N];
	rep(i, N) cin >> A[i];
	rep(i, N) cin >> B[i];
	sort(A, A + N);
	sort(B, B + N);
	int A_win = 0;
	int cnt = 0;
	do {
		int C[N];
		rep(i, N) C[i] = B[i];
		do {
			int tmpA = 0;
			int tmpB = 0;
			cnt++;
			rep(i, N) {
				if (A[i] > C[i]) tmpA++;
				else  tmpB++;
			}
			if (tmpA > tmpB) A_win++;
		} while (next_permutation(B, B + N));
	} while (next_permutation(A, A + N));
	cout << (double)A_win / cnt << endl;

	return 0;
}