/*

Code for problem F by cookiedoth
Generated 14 Aug 2020 at 04.58 PM


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───▄▄██▌█░ВЕЗЁМ▄▀▀▀▄░ГУСЕЙ░░░░░░░
───████▌█▄███▀░◐░▄▀▀▀▄░░РАБОТЯГИ░
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▀(@)▀▀▀▀▀▀▀(@)(@)▀▀▀▀▀▀▀▀▀▀▀▀▀(@)▀(@)

=_=
¯\_(ツ)_/¯
^_^

*/

#include <iostream>
#include <fstream>
#include <vector>
#include <set>
#include <map>
#include <bitset>
#include <algorithm>
#include <iomanip>
#include <cmath>
#include <ctime>
#include <functional>
#include <unordered_set>
#include <unordered_map>
#include <string>
#include <queue>
#include <deque>
#include <stack>
#include <complex>
#include <cassert>
#include <random>
#include <cstring>
#include <numeric>
#define ll long long
#define ld long double
#define null NULL
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define debug(a) cerr << #a << " = " << a << endl
#define forn(i, n) for (int i = 0; i < n; ++i)
#define sz(a) (int)a.size()

using namespace std;

template<class T> int chkmax(T &a, T b) {
	if (b > a) {
		a = b;
		return 1;
	}
	return 0;
}

template<class T> int chkmin(T &a, T b) {
	if (b < a) {
		a = b;
		return 1;
	}
	return 0;
}

template<class iterator> void output(iterator begin, iterator end, ostream& out = cerr) {
	while (begin != end) {
		out << (*begin) << " ";
		begin++;
	}
	out << endl;
}

template<class T> void output(T x, ostream& out = cerr) {
	output(x.begin(), x.end(), out);
}

void fast_io() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
}

const int mx = 1e5 + 228;
int n;
ld p[mx], q[mx], t[mx];
int A[mx];

void read() {
	cin >> n;
	for (int i = 0; i < n; ++i) {
		cin >> p[i];
	}
	for (int i = 0; i < n; ++i) {
		cin >> q[i];
	}
	for (int i = 0; i < n; ++i) {
		cin >> A[i];
	}
}

int check(ld tb) {
	ld tb2 = 0;
	for (int i = 0; i < n; ++i) {
		t[i] = (1.0 - q[i]) / (1.0 - q[i] * tb);
		tb2 += p[i] * t[i];
	}
	// cerr << "tb/tb2 " << tb << " " << tb2 << endl;
	return (tb < tb2);
}

void solve() {
	ld l = 0, r = 1;
	for (int it = 0; it < 80; ++it) {
		ld mid = (l + r) / 2;
		if (check(mid)) {
			l = mid;
		} else {
			r = mid;
		}
	}
	check(l);
	// cout << l << '\n';
}

signed main() {
	fast_io();
	read();
	// for (ld i = 0.0; i <= 1.0; i += 0.01) {
	// 	check(i);
	// }
	solve();
	ld ans = 0.0;
	for (int i = 0; i < n; ++i) {
		ans += logl(t[i]) * (ld)A[i];
	}
	cout << setprecision(10) << fixed << ans << '\n';
}