Assign list elements to matrix
A challenge can hide secrets M00 = M01 = M10 = M11 = M20 = M21 = 0
M[0][0] = 'A' M[0][1] = 'challenge' M[1][0] = 'can' M[1][1] = 'hide' M[2][0] = 'secrets' M[2][1] = 0