#include <bits/stdc++.h>
using namespace std;
int tux;
int foo = 0, bar = 0, baz = 0, quz = 0;
int pur;
int main() {
  cin >> tux;
  for (; tux > 0; tux--) {
    cin >> pur;
    foo = foo + pur;
    bar = bar + 1;
    if (max(foo * quz, bar * baz) == foo * quz) {
      baz = foo;
      quz = bar;
    }
  }
  double ans = (double)baz / (double)quz;
  printf("%.12lf", ans);
  return 0;
}
