A compound represented by the formula (Ia-34): wherein R 1 is a phenyl group, a cyclopentyl group, a cyclohexyl group, a pyrrolyl group, a pyrazolyl group, a thiazolyl group, an imidazolyl group, an oxazolyl group, a thienyl group, a furyl group, a pyridyl group, a pyrrolidinyl group or a piperidyl group, each of which is optionally substituted by 1 to 3 substituents selected from (i) a halogen atom, (ii) hydroxy, (iii) cyano, (iv) C 1-6 alkyl optionally substituted by 1 - 5 halogen atoms, (v) C 1-6 alkoxy optionally substituted by 1 - 5 halogen atoms, (vi) amino optionally mono- or di-substituted by C 1-6 alkyl, (vii) oxo, (viii) carbamoyl, (ix) mono-C 1-6 alkyl-carbamoyl, (x) di-C 1-6 alkyl-carbamoyl, (xi) C 1-6 alkylsulfonyl and (xii)C 1-6 alkyl-carbonylamino; R 2 is a phenyl group, a cyclopentyl group, a cyclohexyl group, a pyrrolyl group, a pyrazolyl group, a thiazolyl group, an imidazolyl group, an oxazolyl group, a thienyl group, a furyl group, a pyridyl group, a pyrrolidinyl group or a piperidyl group, each of which is optionally substituted by 1 to 3 substituents selected from a halogen atom, a cyano group, a trifluoromethyl group, a methyl group, an ethyl group and a methoxy group; R 3 and R 4 are the same or different and each is a hydrogen atom or a methyl group, or R 3 and R 4 may form, together with the adjacent nitrogen atom, nitrogen-containing heterocycle optionally substituted by hydroxy; R 13 is a hydrogen atom, a halogen atom, a methyl group or a cyano group; and Y is -CH 2 -, -CH(CH 3 )-, -C(CH 3 ) 2 -, -CO-, -CH(OH)-, -O-, -NH-,-N(CH 3 )-, -S-, -SO-, -SO 2 -CH 2 -, -SO 2 -C(CH 3 ) 2 -, -SO 2 -NH- or -SO 2 -N(CH 3 )-, or a salt thereof. R 1 is a phenyl group, a cyclopentyl group, a cyclohexyl group, a pyrrolyl group, a pyrazolyl group, a thiazolyl group, an imidazolyl group, an oxazolyl group, a thienyl group, a furyl group, a pyridyl group, a pyrrolidinyl group or a piperidyl group, each of which is optionally substituted by 1 to 3 substituents selected from (i) a halogen atom, (ii) hydroxy, (iii) cyano, (iv) C 1-6 alkyl optionally substituted by 1 - 5 halogen atoms, (v) C 1-6 alkoxy optionally substituted by 1 - 5 halogen atoms, (vi) amino optionally mono- or di-substituted by C 1-6 alkyl, (vii) oxo, (viii) carbamoyl, (ix) mono-C 1-6 alkyl-carbamoyl, (x) di-C 1-6 alkyl-carbamoyl, (xi) C 1-6 alkylsulfonyl and (xii)C 1-6 alkyl-carbonylamino; R 2 is a phenyl group, a cyclopentyl group, a cyclohexyl group, a pyrrolyl group, a pyrazolyl group, a thiazolyl group, an imidazolyl group, an oxazolyl group, a thienyl group, a furyl group, a pyridyl group, a pyrrolidinyl group or a piperidyl group, each of which is optionally substituted by 1 to 3 substituents selected from a halogen atom, a cyano group, a trifluoromethyl group, a methyl group, an ethyl group and a methoxy group; R 3 and R 4 are the same or different and each is a hydrogen atom or a methyl group, or R 3 and R 4 may form, together with the adjacent nitrogen atom, nitrogen-containing heterocycle optionally substituted by hydroxy; R 13 is a hydrogen atom, a halogen atom, a methyl group or a cyano group; and Y is -CH 2 -, -CH(CH 3 )-, -C(CH 3 ) 2 -, -CO-, -CH(OH)-, -O-, -NH-,-N(CH 3 )-, -S-, -SO-, -SO 2 -CH 2 -, -SO 2 -C(CH 3 ) 2 -, -SO 2 -NH- or -SO 2 -N(CH 3 )-, <EOS>