#include <bits/stdc++.h>
using namespace std;
const long long oo = 0x3f3f3f3f3f3f3f3f;
const double eps = 1e-9;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long n;
  cin >> n;
  vector<double> p(n);
  for (long long i = (0); i < (n); i++) cin >> p[i], p[i] /= 100;
  const long long N = 300000;
  vector<double> pr(N + 1);
  vector<double> q(n);
  for (long long i = (0); i < (n); i++) q[i] = 1 - p[i];
  pr[n] = 1;
  for (long long i = (0); i < (n); i++) pr[n] *= p[i];
  priority_queue<pair<double, long long>> pq;
  for (long long i = (0); i < (n); i++)
    pq.push({(1 - q[i] * (1 - p[i])) / (1 - q[i]), i});
  for (long long k = (n + 1); k < (N + 1); k++) {
    double fac;
    long long i;
    tie(fac, i) = pq.top();
    pq.pop();
    pr[k] = fac * pr[k - 1];
    q[i] *= 1 - p[i];
    pq.push({(1 - q[i] * (1 - p[i])) / (1 - q[i]), i});
  }
  double res = N * pr[N];
  for (long long k = (0); k < (N); k++) res -= pr[k];
  cout << fixed << setprecision(12) << res << endl;
}
