Score : 200 points
You are given a string S consisting of lowercase English letters.
Find the lexicographically (alphabetically) smallest lowercase English letter that does not occur in S.
If every lowercase English letter occurs in S, print None
instead.
Input is given from Standard Input in the following format:
S
Print the lexicographically smallest lowercase English letter that does not occur in S.
If every lowercase English letter occurs in S, print None
instead.
atcoderregularcontest
b
The string atcoderregularcontest
contains a
, but does not contain b
.
abcdefghijklmnopqrstuvwxyz
None
This string contains every lowercase English letter.
fajsonlslfepbjtsaayxbymeskptcumtwrmkkinjxnnucagfrg
d