#include <bits/stdc++.h>
using namespace std;
struct node {
  double now, nxt, p;
  node(double now = 0, double nxt = 0, double p = 0)
      : now(now), nxt(nxt), p(p) {}
  bool operator<(const node &a) const { return nxt / now < a.nxt / a.now; }
};
int main() {
  int n;
  while (~scanf("%d", &n)) {
    priority_queue<node> pque;
    double pro = 1;
    for (int i = 0; i < n; ++i) {
      int x;
      scanf("%d", &x);
      double p = x / 100.0;
      pro *= p;
      pque.push(node(p, 1 - (1 - p) * (1 - p), 1 - p));
    }
    double ans = n * pro;
    for (int i = n + 1; i < 1000000; ++i) {
      node u = pque.top();
      pque.pop();
      double tmp = pro * u.nxt / u.now;
      ans += i * (tmp - pro);
      pro = tmp;
      u.now = u.nxt;
      u.nxt = 1 - (1 - u.now) * u.p;
      pque.push(u);
    }
    printf("%.10f\n", ans);
  }
  return 0;
}
