#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 ld = long double;
using V = vector<int>;
using Vld = vector<ld>;

int main() {
  int 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];

  ld y = 0;
  rep(i, 100) {
    ld f = 0;
    rep(i, n) f += p[i] * (1-q[i]) / (1-q[i]*y);
    y = f;
  }

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