Group(), Groups() & Groupdict() - Hacker Rank Solution

Group(), Groups() & Groupdict() - Hacker Rank Solution

[A-Za-z0-9])\1+ can be used to solve this problem.
The expression ([A-Za-z0-9]) will match an alphanumeric character and store it in group .
The expression \1 matches the exact same text that was matched by the first capturing group.

import re
m = re.search(r'([A-Za-z0-9])\1+',raw_input())
if m:
    print m.group(1)
else:
    print -1