With a given matrix A (size m x n) create a matrix B (size m+2 x n+2) so that the matrix A is surrounded by ones:

A = [1 2 3
     3 2 1]
B = [1 1 1 1 1
     1 1 2 3 1
     1 3 2 1 1
     1 1 1 1 1]

or

A = 4
B = [ 1 1 1
      1 4 1
      1 1 1]

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Last Solution submitted on Feb 28, 2026

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