import re
def remove_reps(s):
while True:
newS = re.sub(r'(.)(.*?)\1', r'\g<2>', s)
if newS == s:
break
s = newS
return newS
print(remove_reps('abbcabb'))
print(remove_reps('abca'))
aW1wb3J0IHJlCgpkZWYgcmVtb3ZlX3JlcHMocyk6Cgl3aGlsZSBUcnVlOgoJCW5ld1MgPSByZS5zdWIocicoLikoLio/KVwxJywgcidcZzwyPicsIHMpCgkJaWYgbmV3UyA9PSBzOgoJCQlicmVhawoJCXMgPSBuZXdTCglyZXR1cm4gbmV3UwoKcHJpbnQocmVtb3ZlX3JlcHMoJ2FiYmNhYmInKSkKcHJpbnQocmVtb3ZlX3JlcHMoJ2FiY2EnKSk=