#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int main() {
	int n;
	int a[4], b[4];
	
	cin >> n;
	REP(i, n) scanf("%d", a + i);
	REP(i, n) scanf("%d", b + i);
	
	sort(a, a + n);
	
	int pat = 0, win = 0;
	do {
		pat++;
		
		int cnt = 0, sum = 0;
		REP(i, n) {
			if (a[i] > b[i]) cnt++;
			if (a[i] != b[i]) sum++;
		}
		
		if (sum / 2 < cnt) win++;
	} while (next_permutation(a, a + n));
	
	printf("%.10f\n", (double)win / pat);
	
	return 0;
}