import re


def escape_html_syntax_characters(string):
  """
  Escape the three HTML syntax characters &, <, >.
    & becomes &amp;
    < becomes &lt;
    > becomes &gt;
  """
  
  string = re.sub('&', '&amp;', string)
  string = re.sub('<', '&lt;', string)
  string = re.sub('>', '&gt;', string)
  
  return string