#include <bits/stdc++.h>
using namespace std;
int tux, foo, bar, baz, quz;
int main() {
  cin >> tux;
  foo = bar = baz = 0;
  quz = 1;
  while (tux > 0) {
    int pur;
    cin >> pur;
    foo += pur;
    bar += 1;
    if (foo * quz > bar * baz) {
      baz = foo;
      quz = bar;
    }
    tux--;
  }
  cout << (double(baz) / quz) << endl;
  return 0;
}
