def second_smallest(numbers):
  if (len(numbers)<2):
    return
  if ((len(numbers)==2)  and (numbers[0] == numbers[1]) ):
    return
  dup_items = set()
  uniq_items = []
  for x in numbers:
    if x not in dup_items:
      uniq_items.append(x)
      dup_items.add(x)
  uniq_items.sort()    
  return  uniq_items[1] 