#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:100000000")
using namespace std;
double x[100100], f[100100];
int main() {
  int n, i, j, k;
  for (scanf("%d", &n), i = 0; i < n;
       scanf("%lf", &x[i]), x[i] /= 100, f[i] = x[i], i++)
    ;
  if (n == 1) {
    printf("1.0\n");
    return 0;
  }
  double p, r = 0;
  p = 1;
  for (k = 0; k < n; p *= f[k], k++)
    ;
  r = n * p;
  for (i = n + 1; i < 400000; i++) {
    p = 0;
    for (k = 0; k < n; k++)
      if ((1 - f[k]) * x[k] / f[k] > p) {
        j = k;
        p = (1 - f[k]) * x[k] / f[k];
      }
    p = 1;
    for (k = 0; k < n && p > 1E-40; k++)
      if (k == j)
        p *= (1 - f[j]) * x[j];
      else
        p *= f[k];
    r += p * i;
    f[j] += (1 - f[j]) * x[j];
  }
  printf("%.13lf\n", r);
  return 0;
}
