regex_group.py

"""

group()

A group() expression returns one or more subgroups of the match. 
Code

>>> import re
>>> m = re.match(r'(\w+)@(\w+)\.(\w+)','username@hackerrank.com')
>>> m.group(0)       # The entire match 
'username@hackerrank.com'
>>> m.group(1)       # The first parenthesized subgroup.
'username'
>>> m.group(2)       # The second parenthesized subgroup.
'hackerrank'
>>> m.group(3)       # The third parenthesized subgroup.
'com'
>>> m.group(1,2,3)   # Multiple arguments give us a tuple.
('username', 'hackerrank', 'com')
groups()

A groups() expression returns a tuple containing all the subgroups of the match. 
Code

>>> import re
>>> m = re.match(r'(\w+)@(\w+)\.(\w+)','username@hackerrank.com')
>>> m.groups()
('username', 'hackerrank', 'com')
groupdict()

A groupdict() expression returns a dictionary containing all the named subgroups of the match, keyed by the subgroup name. 
Code

>>> m = re.match(r'(?P<user>\w+)@(?P<website>\w+)\.(?P<extension>\w+)','myname@hackerrank.com')
>>> m.groupdict()
{'website': 'hackerrank', 'user': 'myname', 'extension': 'com'}
Task

You are given a string SS. 
Your task is to find the first occurrence of an alphanumeric character in SS (read from left to right) that has consecutive repetitions.

Input Format

A single line of input containing the string SS.

Constraints

0<len(S)<1000<len(S)<100
Output Format

Print the first occurrence of the repeating character. If there are no repeating characters, print -1.

Sample Input

..12345678910111213141516171820212223
Sample Output

1
Explanation

.. is the first repeating character, but it is not alphanumeric. 
1 is the first (from left to right) alphanumeric repeating character of the string in the substring 111.

"""



import re
m = re.search(r'([a-zA-Z0-9])\1',raw_input())
if m:
    print m.groups()[0]
else:
    print -1