#include <bits/stdc++.h>
using namespace std;
const int N = 100;
int n, k[N];
double p[N], p_log[N], p_log_1[N];
priority_queue<pair<double, int>> s;
inline double P(int i, int k) {
  double x = pow(p[i], k);
  if (x > 1e-6) return log(1 - x);
  x = -x;
  return x - x * x / 2 + x * x * x / 3;
}
void add(int i) { s.push(make_pair(P(i, k[i] + 1) - P(i, k[i]), i)); }
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0);
  cin >> n;
  if (n == 1) {
    puts("1");
    return 0;
  }
  for (int i = 0; i < (int)(n); i++) {
    int a;
    cin >> a;
    p[i] = 1 - a * 1e-2;
    p_log[i] = log(p[i]);
    p_log_1[i] = log(1 - p[i]);
  }
  double sum = 0;
  int cnt = n;
  for (int i = 0; i < (int)(n); i++) sum += P(i, k[i] = 1);
  double res = exp(sum) * cnt;
  for (int i = 0; i < (int)(n); i++) add(i);
  while (cnt <= 1e6) {
    cnt++;
    int i = s.top().second;
    s.pop();
    sum -= P(i, k[i]);
    double x = cnt * exp(sum + p_log[i] * k[i]) * (1 - p[i]);
    res += x;
    sum += P(i, ++k[i]);
    add(i);
  }
  printf("%.15f\n", (double)res);
  fprintf(stderr, "time = %.2f, cnt = %d\n", 1. * clock() / CLOCKS_PER_SEC,
          cnt);
  return 0;
}
