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>a</name><arg><funapp><name>b</name><arg><funapp><name>c</name><arg><var>x1</var></arg></funapp></arg></funapp></arg></funapp></lhs><rhs><funapp><name>c</name><arg><funapp><name>b</name><arg><funapp><name>a</name><arg><var>x1</var></arg></funapp></arg></funapp></arg></funapp></rhs></rule><rule><lhs><funapp><name>a</name><arg><funapp><name>c</name><arg><var>x1</var></arg></funapp></arg></funapp></lhs><rhs><funapp><name>a</name><arg><funapp><name>a</name><arg><funapp><name>d</name><arg><funapp><name>a</name><arg><var>x1</var></arg></funapp></arg></funapp></arg></funapp></arg></funapp></rhs></rule><rule><lhs><funapp><name>d</name><arg><funapp><name>a</name><arg><funapp><name>b</name><arg><var>x1</var></arg></funapp></arg></funapp></arg></funapp></lhs><rhs><funapp><name>b</name><arg><funapp><name>a</name><arg><funapp><name>d</name><arg><var>x1</var></arg></funapp></arg></funapp></arg></funapp></rhs></rule><rule><lhs><funapp><name>d</name><arg><funapp><name>a</name><arg><funapp><name>c</name><arg><var>x1</var></arg></funapp></arg></funapp></arg></funapp></lhs><rhs><funapp><name>b</name><arg><funapp><name>c</name><arg><funapp><name>c</name><arg><var>x1</var></arg></funapp></arg></funapp></arg></funapp></rhs></rule></rules></trs></trsInput></input><cpfVersion>2.1</cpfVersion><proof><trsNonterminationProof><nonterminatingSRS><derivationPatterns><derivationPatternProof><OC1><overlapClosureSRS><string><name>a</name><name>b</name><name>c</name></string><string><name>c</name><name>b</name><name>a</name></string></overlapClosureSRS><isPair>false</isPair></OC1></derivationPatternProof><derivationPatternProof><OCintoDP1><derivationPattern><wordPattern><string/><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>c</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>0</constant><string/></wordPattern></derivationPattern><overlapClosureSRS><string><name>a</name><name>b</name><name>c</name></string><string><name>c</name><name>b</name><name>a</name></string></overlapClosureSRS></OCintoDP1></derivationPatternProof><derivationPatternProof><lift><derivationPattern><wordPattern><string/><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>c</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string/></wordPattern></derivationPattern><derivationPattern><wordPattern><string/><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>c</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>0</constant><string/></wordPattern></derivationPattern></lift></derivationPatternProof><derivationPatternProof><equivalent><derivationPattern><wordPattern><string/><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>c</name><name>b</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string><name>a</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string/><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>c</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string/></wordPattern></derivationPattern></equivalent></derivationPatternProof><derivationPatternProof><OC1><overlapClosureSRS><string><name>a</name><name>c</name></string><string><name>a</name><name>a</name><name>d</name><name>a</name></string></overlapClosureSRS><isPair>false</isPair></OC1></derivationPatternProof><derivationPatternProof><DP_OC_1_2><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name><name>d</name><name>a</name><name>b</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string><name>a</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string/><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>c</name><name>b</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string><name>a</name></string></wordPattern></derivationPattern><overlapClosureSRS><string><name>a</name><name>c</name></string><string><name>a</name><name>a</name><name>d</name><name>a</name></string></overlapClosureSRS><string><name>a</name></string><string><name>b</name></string><string><name>c</name></string></DP_OC_1_2></derivationPatternProof><derivationPatternProof><equivalent><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name><name>d</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>a</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name><name>d</name><name>a</name><name>b</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string><name>a</name></string></wordPattern></derivationPattern></equivalent></derivationPatternProof><derivationPatternProof><OC1><overlapClosureSRS><string><name>d</name><name>a</name><name>b</name></string><string><name>b</name><name>a</name><name>d</name></string></overlapClosureSRS><isPair>false</isPair></OC1></derivationPatternProof><derivationPatternProof><OCintoDP2><derivationPattern><wordPattern><string><name>d</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string/></wordPattern><wordPattern><string/><string><name>b</name><name>a</name></string><factor>1</factor><constant>0</constant><string><name>d</name></string></wordPattern></derivationPattern><overlapClosureSRS><string><name>d</name><name>a</name><name>b</name></string><string><name>b</name><name>a</name><name>d</name></string></overlapClosureSRS></OCintoDP2></derivationPatternProof><derivationPatternProof><lift><derivationPattern><wordPattern><string><name>d</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string/></wordPattern><wordPattern><string/><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string><name>d</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string><name>d</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>0</constant><string/></wordPattern><wordPattern><string/><string><name>b</name><name>a</name></string><factor>1</factor><constant>0</constant><string><name>d</name></string></wordPattern></derivationPattern></lift></derivationPatternProof><derivationPatternProof><DP_DP_1_1><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string><name>d</name><name>a</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name><name>d</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>a</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string><name>d</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string/></wordPattern><wordPattern><string/><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string><name>d</name></string></wordPattern></derivationPattern><string><name>a</name><name>a</name></string><string><name>a</name></string></DP_DP_1_1></derivationPatternProof><derivationPatternProof><OC1><overlapClosureSRS><string><name>d</name><name>a</name><name>c</name></string><string><name>b</name><name>c</name><name>c</name></string></overlapClosureSRS><isPair>false</isPair></OC1></derivationPatternProof><derivationPatternProof><DP_OC_3_2><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string><name>b</name><name>c</name><name>c</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string><name>d</name><name>a</name></string></wordPattern></derivationPattern><overlapClosureSRS><string><name>d</name><name>a</name><name>c</name></string><string><name>b</name><name>c</name><name>c</name></string></overlapClosureSRS><string/><string><name>c</name></string><string><name>d</name><name>a</name></string></DP_OC_3_2></derivationPatternProof><derivationPatternProof><equivalent><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name><name>c</name></string></wordPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>2</constant><string><name>c</name><name>c</name></string></wordPattern></derivationPattern><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name><name>c</name></string></wordPattern><wordPattern><string><name>a</name><name>a</name></string><string><name>b</name><name>a</name></string><factor>1</factor><constant>1</constant><string><name>b</name><name>c</name><name>c</name></string></wordPattern></derivationPattern></equivalent></derivationPatternProof></derivationPatterns><selfEmbeddingDP><derivationPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>1</constant><string><name>c</name><name>c</name></string></wordPattern><wordPattern><string><name>a</name></string><string><name>a</name><name>b</name></string><factor>1</factor><constant>2</constant><string><name>c</name><name>c</name></string></wordPattern></derivationPattern><string/><string/></selfEmbeddingDP></nonterminatingSRS></trsNonterminationProof></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>