The present invention relates to a compound represented by the formula: wherein A is pyridyl group having at least one substituent wherein R1, R2 and R3 are each a hydrogen atom, a halogen atom, a C1-6 alkyl group optionally substituted by halogen or a C1-6 alkoxy group optionally substituted by halogen, R4 and R6 are each a hydrogen atom, a halogen atom or a C1-6 alkyl group optionally substituted by halogen, R5 is a hydrogen atom, a halogen atom, a C1-6 alkyl group optionally substituted by halogen or a C1-6 alkoxy group optionally substituted by halogen, and R7 is a hydrogen atom or a C1-6 alkyl group optionally substituted by halogen or a salt thereof, or a pharmaceutical composition containing the same.