NO
<?xml version="1.0" encoding="UTF-8" standalone="no"?><?xml-stylesheet type="text/xsl" href="cpfHTML.xsl"?><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><var>x</var></arg></funapp></lhs><rhs><funapp><name>f</name><arg><var>x</var></arg><arg><funapp><name>f</name><arg><funapp><name>b</name></funapp></arg><arg><var>x</var></arg></funapp></arg></funapp></rhs></rule></rules></trs><relativeRules><rules><rule><lhs><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x</var></arg><arg><var>y</var></arg></funapp></arg><arg><var>z</var></arg></funapp></lhs><rhs><funapp><name>f</name><arg><var>x</var></arg><arg><funapp><name>f</name><arg><var>y</var></arg><arg><var>z</var></arg></funapp></arg></funapp></rhs></rule><rule><lhs><funapp><name>f</name><arg><var>x</var></arg><arg><funapp><name>f</name><arg><var>y</var></arg><arg><var>z</var></arg></funapp></arg></funapp></lhs><rhs><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x</var></arg><arg><var>y</var></arg></funapp></arg><arg><var>z</var></arg></funapp></rhs></rule></rules></relativeRules></trsInput></input><cpfVersion>2.1</cpfVersion><proof><relativeNonterminationProof><loop><rewriteSequence><startTerm><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><funapp><name>f</name><arg><var>x'</var></arg><arg><funapp><name>f</name><arg><var>y'</var></arg><arg><funapp><name>a</name></funapp></arg></funapp></arg></funapp></arg></funapp></startTerm><rewriteStep><positionInTerm><position>2</position></positionInTerm><rule><lhs><funapp><name>f</name><arg><var>x</var></arg><arg><funapp><name>f</name><arg><var>y</var></arg><arg><var>z</var></arg></funapp></arg></funapp></lhs><rhs><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x</var></arg><arg><var>y</var></arg></funapp></arg><arg><var>z</var></arg></funapp></rhs></rule><relative/><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x'</var></arg><arg><var>y'</var></arg></funapp></arg><arg><funapp><name>a</name></funapp></arg></funapp></arg></funapp></rewriteStep><rewriteStep><positionInTerm/><rule><lhs><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><var>x</var></arg></funapp></lhs><rhs><funapp><name>f</name><arg><var>x</var></arg><arg><funapp><name>f</name><arg><funapp><name>b</name></funapp></arg><arg><var>x</var></arg></funapp></arg></funapp></rhs></rule><funapp><name>f</name><arg><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x'</var></arg><arg><var>y'</var></arg></funapp></arg><arg><funapp><name>a</name></funapp></arg></funapp></arg><arg><funapp><name>f</name><arg><funapp><name>b</name></funapp></arg><arg><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x'</var></arg><arg><var>y'</var></arg></funapp></arg><arg><funapp><name>a</name></funapp></arg></funapp></arg></funapp></arg></funapp></rewriteStep><rewriteStep><positionInTerm/><rule><lhs><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x</var></arg><arg><var>y</var></arg></funapp></arg><arg><var>z</var></arg></funapp></lhs><rhs><funapp><name>f</name><arg><var>x</var></arg><arg><funapp><name>f</name><arg><var>y</var></arg><arg><var>z</var></arg></funapp></arg></funapp></rhs></rule><relative/><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x'</var></arg><arg><var>y'</var></arg></funapp></arg><arg><funapp><name>f</name><arg><funapp><name>a</name></funapp></arg><arg><funapp><name>f</name><arg><funapp><name>b</name></funapp></arg><arg><funapp><name>f</name><arg><funapp><name>f</name><arg><var>x'</var></arg><arg><var>y'</var></arg></funapp></arg><arg><funapp><name>a</name></funapp></arg></funapp></arg></funapp></arg></funapp></arg></funapp></rewriteStep></rewriteSequence><substitution><substEntry><var>x'</var><funapp><name>b</name></funapp></substEntry><substEntry><var>y'</var><funapp><name>f</name><arg><var>x'</var></arg><arg><var>y'</var></arg></funapp></substEntry></substitution><funContext><name>f</name><before><funapp><name>f</name><arg><var>x'</var></arg><arg><var>y'</var></arg></funapp></before><box/><after/></funContext></loop></relativeNonterminationProof></proof><origin><proofOrigin><tool><name>AProVE</name><version>AProVE Commit ID: 48fb2092695e11cc9f56e44b17a92a5f88ffb256 marcel 20180622 unpublished dirty
</version><strategy>Statistics for single proof: 100.00 % (1 real / 0 unknown / 0 assumptions / 1 total proof steps)</strategy><url>http://aprove.informatik.rwth-aachen.de</url></tool><toolUser><firstName>John</firstName><lastName>Doe</lastName></toolUser></proofOrigin><inputOrigin/></origin></certificationProblem>