#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int foo = 0, bar = 0, baz = 0, quz = 1;
  for (int i = 0; i < n; i++) {
    int pur;
    cin >> pur;
    foo = foo + pur;
    bar = bar + 1;
    if (max(foo * quz, bar * baz) == max(baz, foo * quz)) {
      baz = foo;
      quz = bar;
    } else {
    }
  }
  double res;
  res = (double)baz / quz;
  printf("%.6lf", res);
  return 0;
}
