#include <bits/stdc++.h>
using namespace std;
const int inf = (int)1e9;
const int mod = inf + 7;
const double pi = acos(-1.0);
const double eps = 1e-12;
int tux, pur, foo = 0, bar = 0, baz = 0, quz = 1;
int main() {
  cin >> tux;
  for (int i = tux; i != 0; i--) {
    cin >> pur;
    foo = foo + pur;
    bar = bar + 1;
    if (max(foo * quz, bar * baz) == foo * quz) {
      baz = foo;
      quz = bar;
    }
  }
  printf("%.7lf", baz / (quz * 1.0));
  return 0;
}
