#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(int i = (n) - 1; (i) >= 0; --i)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD LL(1e9 + 7)
#define INF 100000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;


int main() {
	int n;
	cin >> n;
	int a[10], b[10], c[10];
	REP(i, n) cin >> a[i];
	REP(i, n) cin >> b[i];
	iota(c, c + n, 0);
	double ans = 0;
	int q = 0;
	do {
		int cnt = 0;
		REP(i, n) {
			if (a[c[i]] > b[i]) cnt++;
			else cnt--;
		}
		if (cnt > 0) ans++;
		q++;
	} while (next_permutation(c, c + n));
	cout << ans / q << endl;
	return 0;
}