revconsappCx1x2rrevconsappx2Cx1rdeeprevappCx1x2restdeeprevappx2Cx1restdeeprevappVnrestrevconsapprestVndeeprevappNrestrestrevconsappVnrrrevconsappNrrdeeprevCx1x2deeprevappCx1x2NdeeprevVnVndeeprevNNsecondVnNsecondCx1x2x2isValCx1x2FalseisValVnTrueisValNFalseisNotEmptyTCx1x2TrueisNotEmptyTVnFalseisNotEmptyTNFalseisEmptyTCx1x2FalseisEmptyTVnFalseisEmptyTNTruefirstVnNfirstCx1x2x1goalxdeeprevxrevconsapp2C2deeprevapp2V1N0deeprev1second1isVal1False0True0isNotEmptyT1isEmptyT1first1goal1INNERMOST