#include <bits/stdc++.h>
using namespace std;
double P[500], PF[500];
double Pref[500], Suff[500];
int main() {
  int n;
  double currp = 1;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> P[i];
    P[i] /= 100;
    PF[i] = 1 - P[i];
    currp *= 1 - PF[i];
  }
  double ans = n;
  for (int i = 1; i <= 500000; i++) {
    double lastp = currp;
    Pref[0] = Suff[n + 1] = 1;
    for (int j = 1; j <= n; j++) Pref[j] = Pref[j - 1] * (1 - PF[j]);
    for (int j = n; j >= 1; j--) Suff[j] = Suff[j + 1] * (1 - PF[j]);
    double bestp = -1;
    int choose = 1;
    for (int j = 1; j <= n; j++) {
      double nowp = Pref[j - 1] * Suff[j + 1] * (1 - PF[j] * (1 - P[j]));
      if (bestp < nowp) {
        bestp = nowp;
        choose = j;
      }
    }
    currp = bestp;
    PF[choose] *= 1 - P[choose];
    ans += i * (currp - lastp);
  }
  cout << fixed << setprecision(20) << ans;
  return 0;
}
