#include <bits/stdc++.h>
using namespace std;
#define rep2(i, m, n) for(int i=int(m); i<int(n); ++i)
#define rep(i, n) rep2(i, 0, n)
using ll = long long;
using ld = long double;
using V = vector<int>;
using Vld = vector<ld>;

int main() {
  ll n; cin >> n;
  Vld p(n), q(n);
  V a(n); 
  rep(i, n) cin >> p[i];
  rep(i, n) cin >> q[i];
  rep(i, n) cin >> a[i];

// assert //
  const ld EPS = 1e-13;
  assert(n >= 1 && n <= int(1e5));
  ld sum = 0;
  rep(i, n) {
    assert(p[i] + EPS >= 1e-6 && p[i] - EPS <= 1);
    sum += p[i];
    assert(q[i] + EPS >= 0.6 && q[i] - EPS <= 0.9);
    assert(a[i] >= 0 && a[i] <= int(1e4));
  }
  assert(sum - EPS <= 1 && sum + EPS >= 1);
/////////// 

  auto fun = [&] (ld y) {
    ld f = 0;
    rep(i, n) f += p[i] * (1-q[i]) / (1-q[i]*y);
    return (f <= y);
  };

  ld ok = 1;
  ld ng = 0;
  rep(i, 30) {
    ld md = (ok + ng) / 2;
    if (fun(md)) ok = md;
    else ng = md;
  }

  ld ans = 0;
  rep(i, n) ans += a[i] * log((1-q[i]) / (1-q[i]*ok));
  cout << ans << endl;
  return 0;
}