#include <bits/stdc++.h>
long double best, ans;
double eps = 1e-9;
int last, now;
double p[105];
int n;
double f[2][105], g[2];
using namespace std;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%lf", &p[i]);
    p[i] /= 100;
  }
  ans = 0;
  int last = 0, now = 1;
  for (int i = 1; i <= 300000; i++) {
    last ^= 1;
    now ^= 1;
    best = 0;
    int w;
    for (int j = 1; j <= n; j++) {
      if ((1 - f[last][j]) * p[j] / f[last][j] > best) {
        best = (1 - f[last][j]) * p[j] / f[last][j];
        w = j;
      }
    }
    for (int j = 1; j <= n; j++) {
      if (j == w) {
        f[now][j] = f[last][j] + (1 - f[last][j]) * p[j];
      } else
        f[now][j] = f[last][j];
    }
    if (f[last][w] < eps) {
      g[now] = 1;
      for (int j = 1; j <= n; j++) g[now] = g[now] * f[now][j];
    } else
      g[now] = g[last] * f[now][w] / f[last][w];
    ans = ans + (g[now] - g[last]) * i;
  }
  printf("%.16lf\n", (double)ans);
  return 0;
}
