Given two integers M, N, generate an M*N matrix. The element value in the matrix is one of the 26 letters from A to Z. A is in the upper left corner, and the remaining numbers are in clockwise direction. Rotate forward and place them incrementally. When it exceeds 26, A starts to fill in. For example, when M=5, N=8, the contents of the matrix are as follows: A B C D E F G H V W X Y Z A B I U J K L M N C JT I H G F E D KS R Q P O N
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Multiple loop implementation