Patent ID: 8247429

Claim:
A compound represented by the formula: wherein R 1 is C 1-6 alkyl or C 3-6 cycloalkyl, R 2 is a hydrogen atom or C 1-6 alkyl, R 3 is a hydrogen atom or C 1-6 alkyl, m is 0, 1 or 2, the tricycle of ring A, ring B and ring C is a ring represented by the formula wherein ring A optionally has 1 or 2 substituents selected from the group consisting of a halogen atom, C 1-6 alkyl, C 6-10 aryl and C 1-6 alkoxy-carbonyl, ring B optionally has one halogen atom, and ring C is unsubstituted, and is a single bond or a double bond, or a salt thereof.