#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i=0; i<int(n); ++i)


int main() {
  int n; cin >> n;
  vector<double> p(n), q(n);
  vector<int> a(n); 
  rep(i, n) cin >> p[i];
  rep(i, n) cin >> q[i];
  rep(i, n) cin >> a[i];

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

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

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