#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
	int n;
	cin >> n;
	vector<int> a(n), b(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	for (int i = 0; i < n; ++i) {
		cin >> b[i];
	}
	int aWinGame = 0;
	int game = 0;
	vector<int> aIndex(n);
	for (int i = 0; i < n; ++i) {
		aIndex[i] = i;
	}
	do {
		vector<int> bIndex(n);
		for (int i = 0; i < n; ++i) {
			bIndex[i] = i;
		}
		do {
			int aWin = 0, bWin = 0;
			for (int turn = 0; turn < n; ++turn) {
				if (a[aIndex[turn]] > b[bIndex[turn]]) {
					++aWin;
				} else if (a[aIndex[turn]] < b[bIndex[turn]]) {
					++bWin;
				}
			}
			if (aWin > bWin) {
				++aWinGame;
			}
			++game;
		} while (next_permutation(bIndex.begin(), bIndex.end()));
	} while (next_permutation(aIndex.begin(), aIndex.end()));
	cout << ((double)aWinGame / (double)game) << endl;
	return 0;
}