{"problem":{"name":"B. Pen spinning accident","description":{"content":"See PDF statement in attachment. ","description_type":"Markdown"},"platform":"Codeforces","limit":{"time_limit":1000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"CF10179B"},"statements":[{"statement_type":"Markdown","content":"See PDF statement in attachment.\n\n[samples]","is_translate":false,"language":"English"},{"statement_type":"Markdown","content":"**Definitions**  \nLet $ s_1, s_2 $ be two palindromic strings over the alphabet $ \\Sigma = \\{a, b, \\dots, z\\} $.  \nLet $ f: \\Sigma \\to \\mathbb{N} $ be the frequency function of the multiset union $ s_1 \\cup s_2 $, i.e., $ f(c) = \\text{count of } c \\text{ in } s_1 + \\text{count of } c \\text{ in } s_2 $.\n\n**Constraints**  \n1. $ |s_1| \\leq 100 $, $ |s_2| \\leq 100 $  \n2. $ s_1 $ and $ s_2 $ are palindromes.  \n\n**Objective**  \nDetermine whether there exists a permutation of the multiset $ s_1 \\cup s_2 $ that forms a palindrome.  \n\nThis is possible if and only if at most one character in $ f $ has an odd frequency.  \n\n$$\n\\boxed{\\text{YES if } \\left| \\left\\{ c \\in \\Sigma \\mid f(c) \\text{ is odd} \\right\\} \\right| \\leq 1 \\text{, otherwise NO}}\n$$","is_translate":false,"language":"Formal"}],"meta":{"iden":"CF10179B","tags":[],"sample_group":[],"created_at":"2026-03-03 11:00:39"}}