Heterocyclic compound

A compound represented by the formula (Ia):

• wherein
• R1 is a C1-6 alkyl group, a C3-10 cycloalkyl group, or a mono-C1-6 alkylamino group;
• r is 0 or 1;
• R2 and R3 are each independently a hydrogen atom, or
• when r is 0, then R2 and R3 may be taken together each other to form a bond;
• R4 is a hydrogen atom;
• R5 is a phenyl group optionally substituted by 1 to 3 halogen atoms;
• R6 and R7 are each independently a hydrogen atom, or a halogen atom;
• X5 is CH or N;
• and
• R12 and R13 are each independently a hydrogen atom, a C1-6 alkyl group, or a halogen atom;
• or a salt thereof.