//
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define lch (o << 1)
#define rch (o << 1 | 1)

typedef double db;
typedef long long ll;
typedef unsigned int ui;
typedef pair<int, int> pint;
typedef tuple<int, int, int> tint;

const int N = 1e5 + 5;
const double EPS = 1e-8;
const int INF = 0x3f3f3f3f;
const ll INF_LL = 0x3f3f3f3f3f3f3f3f;

double p[N], q[N];
int a[N];
int n;

double Cal(double y) {
	double ret = 0;
	for (int i = 1; i <= n; i++)
		ret += p[i] * (1 - q[i]) / (1 - q[i] * y);
	return ret;
}

double BSearch(double L, double R) {
	while (R - L > EPS) {
		double M = (L + R) / 2;
		double fy = Cal(M);
		if (M >= fy)
			R = M;
		else
			L = M;
	}
	return L;
}

int main() {
	ios::sync_with_stdio(0);

	cin >> n;
	for (int i = 1; i <= n; i++)
		cin >> p[i];
	for (int i = 1; i <= n; i++)
		cin >> q[i];
	for (int i = 1; i <= n; i++)
		cin >> a[i];

	double y = BSearch(0, 1);
	double ans = 0;
	for (int i = 1; i <= n; i++) {
		double x = (1 - q[i]) / (1 - q[i] * y);
		ans += a[i] * log(x);
	}
	cout << fixed << setprecision(10) << ans << endl;

	return 0;
}