2ndspossNconsX2ndspossNcons2Z2ndspossNcons2consYrconsposrecipY2ndsnegNZ2ndsnegsNconsX2ndsnegsNcons2Z2ndsnegsNcons2consYrconsnegrecipY2ndsposNZfromXconsX2ndspos0Zrnil2ndsneg0ZrnilpiX2ndsposXfrom0plus0YYplussXYsplusXYtimes0Y0timessXYplusYtimesXYsquareXtimesXX