#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a, b, c, d;
  a = b = c = 0;
  d = 1;
  for (int i = 0; i < n; i++) {
    int tmp = 0;
    scanf("%d", &tmp);
    a += tmp;
    b++;
    if (a * d > b * c) {
      c = a;
      d = b;
    }
  }
  printf("%.6lf\n", double(c) / double(d));
  return 0;
}
