#include <bits/stdc++.h>
int main() {
  int n, pur, foo = 0, quz = 1, bar = 0, baz = 0;
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    scanf("%d", &pur);
    foo += pur, bar++;
    if (foo * quz > bar * baz) quz = bar, baz = foo;
  }
  printf("%.6lf\n", (double)baz / quz);
  return 0;
}
