#include <bits/stdc++.h>
using namespace std;
long double f[300000 + 10], p[110], num[110], now, ans;
int n;
int main() {
  scanf("%d", &n);
  for (int pp, i = 1; i <= n; i++) {
    scanf("%d", &pp);
    p[i] = (long double)(100 - pp) / 100.;
  }
  now = 1.;
  for (int i = 1; i <= n; i++) num[i] = p[i], now *= (1. - num[i]);
  f[n] = now;
  for (int k, j, i = n + 1; i <= 300000; i++) {
    if (abs(now - (long double)1.) < 1e-16) {
      f[i] = now;
      continue;
    }
    long double maxn = 1.;
    for (j = 1; j <= n; j++)
      if (maxn < (1. - num[j] * p[j]) / (1. - num[j]))
        maxn = (1. - num[j] * p[j]) / (1. - num[j]), k = j;
    now *= maxn, f[i] = now;
    num[k] *= p[k];
  }
  for (int i = n; i <= 300000; i++) ans += (long double)i * (f[i] - f[i - 1]);
  printf("%.12lf\n", (double)ans);
}
