def AddOrdinalSuffix(value):
  """Adds an ordinal suffix to a non-negative integer (e.g. 1 -> '1st').

  Args:
    value: A non-negative integer.

  Returns:
    A string containing the integer with a two-letter ordinal suffix.
  """
  if value < 0 or value != int(value):
    raise ValueError('argument must be a non-negative integer: %s' % value)

  if value % 100 in (11, 12, 13):
    suffix = 'th'
  else:
    rem = value % 10
    if rem == 1:
      suffix = 'st'
    elif rem == 2:
      suffix = 'nd'
    elif rem == 3:
      suffix = 'rd'
    else:
      suffix = 'th'

  return str(value) + suffix