The present invention provides a compound represented by formula (I) or a pharmaceutically acceptable salt thereof. [In the formula, R1 is an optionally substituted C1-4 alkyl, n is an integer of 1 to 4, R2 is an optionally substituted C1-4 alkyl or hydrogen atom, R3 is an optionally substituted C1-4 alkyl, R4a, R4b, R4c, and R4d are the same or different and each is an optionally substituted C6-14 aryl, optionally substituted C1-4 alkyl, or hydrogen atom, or the like, and A is an optionally substituted C6-14 aryl or optionally substituted 5-member to 11-member heteroaryl.]
