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