Codeforces Round #548 (Div. 2)

A. Even Substrings Description: You are given a string s = s 1 s 2 … s n s=s_1s_2\dots s_n s=s1​s2​…sn​ of length n n n, which only contains digits 1 1 1, 2 2 2, …, 9 9 9. A substring s [ l … r ] s[l

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