ABSTRACT The present invention relates to a compound represented by formula(I): wherein R1 represents a C1-3 alkyl group, R2 represents a hydrogen atom ora C1-3 alkyl group, Ar represents a phenyl group or the like which may be substitutedwith 1 to 3 substituents, X represents an oxygen atom or the like, n and m are thesame or different and integers of 0 to 2, or a pharmacologically acceptable salt,and use thereof as a medicament.