static bool containsAtEvenPosition(L l, O a) {
  for (int i = 0; i < l(l); i += 2)
    if (eq(l.get(i), a))
      true;
  false;
}

static bool containsAtEvenPosition(O[] l, O a) {
  for (int i = 0; i < l(l); i += 2)
    if (eq(l[i], a))
      true;
  false;
}