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<certificationProblem xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="cpf.xsd"><input><trsInput><trs><rules><rule><lhs><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><funapp><name>b</name></funapp></arg><arg><var>x</var></arg></funapp></lhs><rhs><funapp><name>f</name><arg><var>x</var></arg><arg><var>x</var></arg><arg><var>x</var></arg></funapp></rhs></rule><rule><lhs><funapp><name>a</name></funapp></lhs><rhs><funapp><name>c</name></funapp></rhs></rule></rules></trs></trsInput></input><cpfVersion>2.1</cpfVersion><proof><crDisproof><nonJoinableFork><rewriteSequence><startTerm><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><funapp><name>b</name></funapp></arg><arg><funapp><name>y1</name></funapp></arg></funapp></startTerm><rewriteStep><positionInTerm><position>1</position></positionInTerm><rule><lhs><funapp><name>a</name></funapp></lhs><rhs><funapp><name>c</name></funapp></rhs></rule><funapp><name>f</name><arg><funapp><name>c</name></funapp></arg><arg><funapp><name>b</name></funapp></arg><arg><funapp><name>y1</name></funapp></arg></funapp></rewriteStep></rewriteSequence><rewriteSequence><startTerm><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><funapp><name>b</name></funapp></arg><arg><funapp><name>y1</name></funapp></arg></funapp></startTerm><rewriteStep><positionInTerm /><rule><lhs><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><funapp><name>b</name></funapp></arg><arg><var>x</var></arg></funapp></lhs><rhs><funapp><name>f</name><arg><var>x</var></arg><arg><var>x</var></arg><arg><var>x</var></arg></funapp></rhs></rule><funapp><name>f</name><arg><funapp><name>y1</name></funapp></arg><arg><funapp><name>y1</name></funapp></arg><arg><funapp><name>y1</name></funapp></arg></funapp></rewriteStep></rewriteSequence><capNotUnif /></nonJoinableFork></crDisproof></proof><origin><proofOrigin><tool><name>Hakusan</name><version>0.10</version></tool></proofOrigin></origin></certificationProblem>