Codeforces Round #679 (Div. 2)

傳送門 Codeforces Round #679 (Div. 2)html A n n n 爲偶數，那麼考慮相鄰數對組合爲零，則有 a i × b i + a i + 1 × b i + 1 = 0 a_i\times b_i+a_{i+1}\times b_{i+1}=0 ai​×bi​+ai+1​×bi+1​=0；取 b i = a i + 1 , b i + 1 = − a i b_i=a

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