def check_knight_move(lhs, rhs):
    """check_knight_move checks whether a knight move is ok."""
    col_diff = abs(ord(lhs[0]) - ord(rhs[0]))
    row_diff = abs(int(lhs[1]) - int(rhs[1]))
    return (col_diff == 2 and row_diff == 1) or (col_diff == 1 and row_diff == 2)