#include <bits/stdc++.h>
using namespace std;
int T, a, b, c, d, e, Pur, Foo = 0, Bar = 0, Baz = 0, Quz;
int main() {
  cin >> T;
  Quz = 1;
  for (int i = 1; i <= T; i++) {
    cin >> Pur;
    Foo = Foo + Pur;
    Bar++;
    if (Foo * Quz > Bar * Baz) {
      Baz = Foo;
      Quz = Bar;
    }
  }
  printf("%.6lf", 1.0 * Baz / Quz);
  return 0;
}
