#include <bits/stdc++.h>
using namespace std;
int foo, bar, baz, quz = 1, tux, pur;
int main(int argc, char const *argv[]) {
  cin >> tux;
  for (int i = 1; i <= tux; i++) {
    cin >> pur;
    foo += pur;
    bar++;
    if (foo * quz > baz * bar) {
      baz = foo;
      quz = bar;
    }
  }
  cout << double(baz) / double(quz) << endl;
}
