#include <iostream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <cassert>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <string>
#include <algorithm>
#include <utility>
#define llint long long
#define inf 1e18
#define rep(x, s, t) for(llint (x) = (s); (x) < (t); (x)++)
#define Rep(x, s, t) for(llint (x) = (s); (x) <= (t); (x)++)
#define chmin(x, y) (x) = min((x), (y))
#define chmax(x, y) (x) = max((x), (y))
#define mod 1000000007

using namespace std;
typedef pair<llint, llint> P;

llint n;
double p[100005], q[100005];
llint a[100005];

bool check(double P)
{
	double sum = 0;
	for(int i = 1; i <= n; i++){
		double mul = (1-q[i])/(1-q[i]*P);
		sum += mul * p[i];
	}
	return sum <= P;
}


int main(void)
{
	//ios::sync_with_stdio(0);
	//cin.tie(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 ub = 1, lb = 0, mid;
	for(int i = 0; i < 100; i++){
		mid = (ub+lb)/2;
		if(check(mid)) ub = mid;
		else lb = mid;
	}
	
	double ans = 0;
	for(int i = 1; i <= n; i++){
		double mul = (1-q[i])/(1-q[i]*ub);
		ans += a[i] * log(mul);
	}
	
	printf("%.11f\n", ans);
	
	return 0;
}