#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;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int 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() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  constexpr int M = 1000000;
  int n; cin >> n;
  vector<int> p(n), q(n);
  REP(i, n) cin >> p[i];
  REP(i, n) cin >> q[i];
  priority_queue<pair<double, int>> que;
  vector<double> prob(n);
  REP(i, n) {
    prob[i] = p[i] * q[i] / 100000.;
    que.emplace(prob[i], i);
  }
  double ans = 0;
  for (int t = 1; t <= M; ++t) {
    const int i = que.top().second; que.pop();
    ans += t * prob[i];
    prob[i] *= 1 - q[i] / 100.;
    que.emplace(prob[i], i);
  }
  cout << ans << '\n';
  return 0;
}