#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define chmax(a, b) a = max(a, b);
#define chmin(a, b) a = min(a, b);
using namespace std;
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;

int main() {
    int n;
    cin >> n;
    vector<double> p(n), q(n);
    VI a(n);
    rep(i, n) cin >> p[i];
    rep(i, n) cin >> q[i];
    rep(i, n) cin >> a[i];
    double l = 0, r = 1;
    rep(_, 300) {
        double c = (l + r) / 2;
        double s = 0;
        rep(i, n) s += p[i] * (1 - q[i]) / (1 - c * q[i]);
        (c < s ? l : r) = c;
    }
    vector<double> e(n);
    rep(i, n) {
        e[i] = log(1-q[i]) - log(1-l*q[i]);
    }
    double ans = 0;
    rep(i, n) ans += a[i] * e[i];
    printf("%.10f\n", ans);
}