>Choose m=2 and n=3, then the coordinates of the squares are
>a1, b1, a2, b2, a3, c3. Move the rook from a1 to b1 to b2 to
>b3 to a3 to a2 to a1. Then the total length of the
>horizontal segments (a1 to b1 and b3 to a3) is 2, which is
>is not divisible by 4.
You seem to have ranks and files confused. Ranks are rows, files are columns. So in this case there are 2 rows, 3 columns. The segments a1b1 and b3a3 are therefore vertical. There are 4 horizontal segments, which fits the given result.

Thankyou

sfwc
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