#include <bits/stdc++.h>
using namespace std;
double f[2][110], h[501000], pr;
int n;
double P[110];
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%lf", &P[i]);
    P[i] /= 100.0;
  }
  for (int i = 1; i <= 500000; ++i) {
    int now = i & 1;
    for (int k = 1; k <= n; k++) f[now][k] = 0.0;
    double MA = -1.0;
    int K;
    for (int k = 1; k <= n; ++k) {
      if ((1 - f[now ^ 1][k]) * P[k] / (f[now ^ 1][k] + 0.00000000001) > MA) {
        MA = (1 - f[now ^ 1][k]) * P[k] / f[now ^ 1][k];
        K = k;
      }
      f[now][k] = f[now ^ 1][k];
    }
    f[now][K] += (1.0 - f[now ^ 1][K]) * P[K];
    h[i] = 1.0;
    for (int k = 1; k <= n; k++) h[i] *= f[now][k];
    pr += (double)(((double)i) * (h[i] - h[i - 1]));
  }
  printf("%lf", pr);
}
