PROBLEM TO BE SOLVED : To provide compounds useful as agents in treatment of diseases, including inflammatory diseases, cancer, and AIDS. SOLUTION : The present invention provides compounds of formula (I) and pharmaceutically acceptable salts thereof, and pharmaceutical compositions comprising the compounds. [Y1 is N or CH; R1 is C1-C3 alkyl or the like; R2 and R6 are each independently H or the like; Y3 is N or substituted/unsubstituted C; Y2 is C(O) or the like; and A1 to A4 are N or substituted/unsubstituted C, provided that zero, one or two of A1 to A4 are N.] SELECTED DRAWING : None COPYRIGHT : (C)2019, JPO&INPIT