#include <bits/stdc++.h>
using namespace std;
const long long linf = 1e18 + 5;
const int mod = (int)1e9 + 7;
const int logN = 17;
const int inf = 1e9;
const int N = 2e5 + 5;
int n, x, y, z;
double a[N], d[N];
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%lf", &a[i]);
    a[i] /= 100;
  }
  int t = 0;
  double ans = 0, cur = 1, bef = 0;
  t = n;
  priority_queue<pair<double, int> > pq;
  for (int i = 1; i <= n; i++) {
    cur *= a[i];
    d[i] = a[i];
    pq.push(make_pair((d[i] * (1 - a[i]) + a[i]) / d[i], i));
  }
  ans += (bef = cur) * n;
  while (t++ < 300000) {
    int go = pq.top().second;
    double mul = pq.top().first;
    pq.pop();
    cur *= mul;
    d[go] *= mul;
    pq.push(make_pair((d[go] * (1 - a[go]) + a[go]) / d[go], go));
    ans += (cur - bef) * t;
    bef = cur;
  }
  printf("%.12lf\n", ans);
  return 0;
}
