Provided are compounds having superior TAFIa inhibitory activity. Specifically, there are provided compounds represented by the following formula (I) or pharmaceutically acceptable salts thereof: wherein A is a benzene ring or a pyridine ring; X is the formula —(CH2)—, the formula —(CH2)2—, an oxygen atom, a nitrogen atom or a single bond; Y is the formula —(CH2)3—NH—R3, the formula —(CH2)4—NH—R3 or a 2-aminopyridyl group; R3 is a hydrogen atom, a C1-6 alkyl group, or the formula —CO2R4; R4 is a C1-6 alkyl group, the formula —CHR5OC(O)R6, or a substituent having the structure represented by the following formula Ia; R5 is a C1-6 alkyl group; R6 is a C1-6 alkyl group, a C3-8 cycloalkyl group, or a phenyl group; R7 is a C1-6 alkyl group or a phenyl group; R1 is a hydrogen atom, a halogen atom, a C1-4 alkyl group substituted by 1-3 halogen atoms, a C1-10 alkyl group, a C1-8 alkoxy group, a C3-8 cycloalkyl group, a C3-8 cycloalkoxy group, a C4-14 cycloalkylalkyl group, or a phenyl group; R2 is CO2R8, or a tetrazolyl group; R8 is a hydrogen atom, a C1-10 alkyl group, or a substituent having the structure represented by the following formula Ib or Ic; m and n are each an integer of zero or one.