He has decided that no two neighbouring pieces of his tune will consist of exactly the same sounds (counting repetitions). We will call such a tune good. More formally, let a = a₁,...,a_k be a tune. Then a is good if for any i, j, (1 ≤ i ≤ k-1 and i + 2j-1 ≤ k), the pieces a_i, ..., a_i+j-i and a_i+j,..., a_i+2j-1 do not use exactly the same sounds, i.e., the number of appearances of some sound is different for a_i, ...,a_i+j-1 and for a_i+j, ..., a_i+2j-1.

a_i+j-i 가 아닌 a_i+j-1 인거 같습니다.

-> He has decided that no two neighbouring pieces of his tune will consist of exactly the same sounds (counting repetitions). We will call such a tune good. More formally, let a = a₁,...,a_k be a tune. Then a is good if for any i, j, (1 ≤ i ≤ k-1 and i + 2j-1 ≤ k), the pieces a_i, ..., a_i+j-1 and a_i+j,..., a_i+2j-1 do not use exactly the same sounds, i.e., the number of appearances of some sound is different for a_i, ...,a_i+j-1 and for a_i+j, ..., a_i+2j-1.