#include <bits/stdc++.h>
using namespace std;
const int N = 1e2 + 5;
int n, m, x, y;
const double eps = 1e-12;
double A[N];
struct NODE {
  int x;
  double bef, now;
  friend bool operator<(NODE a, NODE b) {
    return a.bef * b.now > a.now * b.bef;
  }
};
priority_queue<NODE> q;
int main() {
  cin >> n;
  double who = 1;
  for (int i = 1; i <= n; ++i) {
    scanf("%d", &x);
    A[i] = 1 - (double)x / 100;
    q.push((NODE){i, 1 - A[i], 1 - A[i] * A[i]});
    who = who * (1 - A[i]);
  }
  int cnt = n;
  double ans = 0;
  ans += cnt * who;
  for (int i = cnt + 1; i <= 5e5; ++i) {
    NODE now = q.top();
    q.pop();
    ans = ans + (who / now.bef * now.now - who) * i;
    who = who / now.bef * now.now;
    q.push((NODE){now.x, now.now, 1 - (1 - now.now) * A[now.x]});
  }
  printf("%.12lf\n", ans);
}
