
import re
def find_longest(s):
  pos = s.find(' ')
  sub = (s[0: pos] if pos >= 0 else s).lower()
  sub = re.search(r'[a-z]+', sub).group(0)
  if pos < 0:
    return sub
  else:
    sub_next = find_longest(s[pos+1:])
    return sub if len(sub) > len(sub_next) else sub_next


52d2b587c63df80e5267a0c8dd932f88ed00bdcc
<mask token>

<mask token>


def find_longest(s):
    pos = s.find(' ')
    sub = (s[0:pos] if pos >= 0 else s).lower()
    sub = re.search('[a-z]+', sub).group(0)
    if pos < 0:
        return sub
    else:
        sub_next = find_longest(s[pos + 1:])
        return sub if len(sub) > len(sub_next) else sub_next

import re


def find_longest(s):
    pos = s.find(' ')
    sub = (s[0:pos] if pos >= 0 else s).lower()
    sub = re.search('[a-z]+', sub).group(0)
    if pos < 0:
        return sub
    else:
        sub_next = find_longest(s[pos + 1:])
        return sub if len(sub) > len(sub_next) else sub_next


import re
def find_longest(s):
  pos = s.find(' ')
  sub = (s[0: pos] if pos >= 0 else s).lower()
  sub = re.search(r'[a-z]+', sub).group(0)
  if pos < 0:
    return sub
  else:
    sub_next = find_longest(s[pos+1:])
    return sub if len(sub) > len(sub_next) else sub_next

