YES activeU11ttNmarkNactiveU21ttMNmarksplusNMactiveandttXmarkXactiveisNat0markttactiveisNatplusV1V2markandisNatV1isNatV2activeisNatsV1markisNatV1activeplusN0markU11isNatNNactiveplusNsMmarkU21andisNatMisNatNMNactiveU11X1X2U11activeX1X2activeU21X1X2X3U21activeX1X2X3activesXsactiveXactiveplusX1X2plusactiveX1X2activeplusX1X2plusX1activeX2activeandX1X2andactiveX1X2U11markX1X2markU11X1X2U21markX1X2X3markU21X1X2X3smarkXmarksXplusmarkX1X2markplusX1X2plusX1markX2markplusX1X2andmarkX1X2markandX1X2properU11X1X2U11properX1properX2properttokttproperU21X1X2X3U21properX1properX2properX3propersXsproperXproperplusX1X2plusproperX1properX2properandX1X2andproperX1properX2properisNatXisNatproperXproper0ok0U11okX1okX2okU11X1X2U21okX1okX2okX3okU21X1X2X3sokXoksXplusokX1okX2okplusX1X2andokX1okX2okandX1X2isNatokXokisNatXtopmarkXtopproperXtopokXtopactiveX2.1U1120tt03U2133s12plus23and21003active11U11212tt0mark11U213321s11plus212and212isNat1100proper11ok11top11activeisNat0markttactiveU11X1X2U11activeX1X2activeU21X1X2X3U21activeX1X2X3activesXsactiveXactiveplusX1X2plusactiveX1X2activeplusX1X2plusX1activeX2activeandX1X2andactiveX1X2U11markX1X2markU11X1X2U21markX1X2X3markU21X1X2X3smarkXmarksXplusmarkX1X2markplusX1X2plusX1markX2markplusX1X2andmarkX1X2markandX1X2properU11X1X2U11properX1properX2properttokttproperU21X1X2X3U21properX1properX2properX3propersXsproperXproperplusX1X2plusproperX1properX2properandX1X2andproperX1properX2properisNatXisNatproperXproper0ok0U11okX1okX2okU11X1X2U21okX1okX2okX3okU21X1X2X3sokXoksXplusokX1okX2okplusX1X2andokX1okX2okandX1X2isNatokXokisNatXtopmarkXtopproperXtopokXtopactiveX1active111isNat1211002mark1111tt02U11222122U213212223s1221plus22122and22122proper111ok111top121activeU11X1X2U11activeX1X2activeU21X1X2X3U21activeX1X2X3activesXsactiveXactiveplusX1X2plusactiveX1X2activeplusX1X2plusX1activeX2activeandX1X2andactiveX1X2properU11X1X2U11properX1properX2properttokttproperU21X1X2X3U21properX1properX2properX3propersXsproperXproperplusX1X2plusproperX1properX2properandX1X2andproperX1properX2properisNatXisNatproperXproper0ok0U11okX1okX2okU11X1X2U21okX1okX2okX3okU21X1X2X3sokXoksXplusokX1okX2okplusX1X2andokX1okX2okandX1X2isNatokXokisNatXtopokXtopactiveX1active111U11212112U213212213s121plus21112and22122proper121tt02ok1111isNat111002top111activeU11X1X2U11activeX1X2activeU21X1X2X3U21activeX1X2X3activesXsactiveXactiveplusX1X2plusactiveX1X2activeplusX1X2plusX1activeX2activeandX1X2andactiveX1X2properU21X1X2X3U21properX1properX2properX3propersXsproperXproperplusX1X2plusproperX1properX2properandX1X2andproperX1properX2properisNatXisNatproperXisNatokXokisNatX1active153s121proper180isNat172ok161U11200U21310plus230and240AProVEAProVE Commit ID: 48fb2092695e11cc9f56e44b17a92a5f88ffb256 marcel 20180622 unpublished dirty Statistics for single proof: 100.00 % (5 real / 0 unknown / 0 assumptions / 5 total proof steps)http://aprove.informatik.rwth-aachen.deJohnDoe