{"problem":{"name":"Not Found","description":{"content":"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","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc071_b"},"statements":[{"statement_type":"Markdown","content":"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.\n\n## Constraints\n\n*   $1 \\leq |S| \\leq 10^5$ ($|S|$ is the length of string $S$.)\n*   $S$ consists of lowercase English letters.\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$S$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc071_b","tags":[],"sample_group":[["atcoderregularcontest","b\n\nThe string `atcoderregularcontest` contains `a`, but does not contain `b`."],["abcdefghijklmnopqrstuvwxyz","None\n\nThis string contains every lowercase English letter."],["fajsonlslfepbjtsaayxbymeskptcumtwrmkkinjxnnucagfrg","d"]],"created_at":"2026-03-03 11:01:14"}}