The present invention provides a novel compound having P2X3 and/or P2X2/3 receptor antagonism. A compound indicated by formula (I) or a pharmaceutically acceptable salt thereof. In formula (I), Ra and Rb together, and Rd and Re together form an oxo or the like； R4a and R4b are hydrogen or the like； n is 1 or the like； R2 is an aryl or the like； s and s' are 0 or the like； R9 and R9 ' are a halogen or the like； R20a and R20b are hydrogen, an alkyl, or the like； u is 1-4； and R13 is hydrogen or the like.
