#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n; cin >> n;
  vector<double> p(n), q(n);
  REP(i, n) cin >> p[i];
  REP(i, n) cin >> q[i];
  function<double(double)> f = [&](double y) {
    double res = 0;
    REP(i, n) res += p[i] * (1 - q[i]) / (1 - q[i] * y);
    return res;
  };
  double lb = 0, ub = 1;
  REP(_, 20) {
    double mid = (lb + ub) / 2;
    (f(mid) <= mid ? ub : lb) = mid;
  }
  double ans = 0;
  REP(i, n) {
    double x = (1 - q[i]) / (1 - q[i] * ub);
    int a; cin >> a;
    ans += a * log(x);
  }
  cout << ans << '\n';
  return 0;
}