Nitrogen-containing heterocyclic compound

A compound represented by the formula (I):

• wherein
• R1 is an optionally substituted 5- or 6-membered cyclic group or an optionally substituted C1-6 alkyl group;
• R2 and R3 are the same or different and each is a hydrogen atom, a halogen atom, a cyano group, an optionally substituted C1-6 alkyl group, an optionally substituted C1-6 alkoxy group or an optionally substituted C3-6 cycloalkyl group;
• R4 is a halogen atom, a cyano group, an optionally substituted C1-6 alkyl group, an optionally substituted C1-6 alkoxy group, an optionally substituted carbamoyl group or an optionally substituted 3- to 8-membered cyclic group;
• and
• Ring A is an optionally further substituted 6-membered aromatic ring,
• or a salt thereof.