#include <bits/stdc++.h>
int n;
double p = 1;
struct Node {
  double w, s, x;
  bool operator<(const Node &b) const { return w < b.w; }
} a;
std::priority_queue<Node> q;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    int x;
    scanf("%d", &x);
    p *= x / 100.0;
    a.s = a.x = 1 - x / 100.0;
    a.w = (1 - a.s * a.x) / (1 - a.s);
    q.push(a);
  }
  double ans = p * n;
  for (int i = 1 + n; i <= 3e6; ++i) {
    a = q.top();
    q.pop();
    double np = p * a.w;
    ans += (np - p) * i;
    p = np;
    a.s *= a.x;
    a.w = (1 - a.s * a.x) / (1 - a.s);
    q.push(a);
  }
  printf("%.10lf\n", ans);
  return 0;
}
