#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline bool chkmin(T &x, T y) {
  return x > y ? x = y, 1 : 0;
}
template <typename T>
inline bool chkmax(T &x, T y) {
  return x < y ? x = y, 1 : 0;
}
template <typename T>
inline void read(T &x) {
  char ch = getchar();
  int f = 1;
  x = 0;
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  x *= f;
}
template <typename T, typename... Args>
inline void read(T &x, Args &...args) {
  read(x), read(args...);
}
const int B = 3e5;
int n;
long double f[105], p[105];
long double ans, g;
long double calc(int x) { return f[x] + (1 - f[x]) * p[x]; }
int main() {
  read(n);
  int x;
  g = 1;
  for (register int i = 1; i <= n; ++i)
    read(x), p[i] = f[i] = 0.01 * x, g = g * p[i];
  ans = n * g;
  for (register int i = n + 1; i <= B; ++i) {
    int x = 1;
    for (register int j = 2; j <= n; ++j)
      if (calc(j) / f[j] > calc(x) / f[x]) x = j;
    long double ng = g / f[x] * calc(x);
    f[x] = calc(x), ans += (ng - g) * i, g = ng;
  }
  printf("%.10lf\n", double(ans));
  return 0;
}
