#include <bits/stdc++.h>
using namespace std;
int main() {
  double tux, pur, foo = 0, bar = 0, baz = 0, quz = 1;
  scanf("%lf", &tux);
  for (int i = 1; i <= tux; i++) {
    scanf("%lf", &pur);
    foo += pur;
    bar++;
    if (foo * quz > baz * bar) {
      baz = foo;
      quz = bar;
    }
  }
  printf("%0.6lf", baz / quz);
  return 0;
}
