SP8551 ABCD - Colours A, B, C, D

Consider a table with 2 rows and 2N columns (a total of 4N cells). Each cell of the first row is coloured by one of the colours A, B, C, D such that there are no two adjacent cells of the same colour. You have to colour the second row using colours A, B, C, D such that: - There are exactly N cells of each colour (A, B, C and D) in the table. - There are no two adjacent cells of the same colour. (Adjacent cells share a vertical or a horizontal side.) It is guaranteed that the solution, not necessarily unique, will always exist.

\[a natural number N \[a string of 2N letters from the set {A, B, C, D}, representing the first row of the table\]

\[a string of 2N letters from the set {A, B, C, D}, representing the second row of the table\]