#AT1118. B - Not Found
B - Not Found
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B - Not Found
Score : $200$ points
Problem Statement
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.
Constraints
- $1 \leq |S| \leq 10^5$ ($|S|$ is the length of string $S$.)
- $S$ consists of lowercase English letters.
Input
Input is given from Standard Input in the following format:
Output
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