Standard input is empty

Standard output is empty

Traceback (most recent call last):
  File "./prog.py", line 4, in <module>
  File "/usr/lib/python3.7/re.py", line 234, in compile
    return _compile(pattern, flags)
  File "/usr/lib/python3.7/re.py", line 286, in _compile
    p = sre_compile.compile(pattern, flags)
  File "/usr/lib/python3.7/sre_compile.py", line 764, in compile
    p = sre_parse.parse(p, flags)
  File "/usr/lib/python3.7/sre_parse.py", line 930, in parse
    p = _parse_sub(source, pattern, flags & SRE_FLAG_VERBOSE, 0)
  File "/usr/lib/python3.7/sre_parse.py", line 426, in _parse_sub
    not nested and not items))
  File "/usr/lib/python3.7/sre_parse.py", line 507, in _parse
    code = _escape(source, this, state)
  File "/usr/lib/python3.7/sre_parse.py", line 402, in _escape
    raise source.error("bad escape %s" % escape, len(escape))
re.error: bad escape \c at position 0