A compound of the formula or a salt thereof: (wherein R 1 is -N(-R 11)(-R 12), or cyclic amino which may be substituted with 1 to 5 substituents selected from the group consisting of Group G and oxo, R 11 is C 1-6 alkyl, R 12 is C 1-6 alkyl which may be substituted with 1 to 5 substituents selected from substituents (b) to (o) of the Group G, or C 3-8 cycloalkyl which may be substituted with 1 to 5 substituents selected from the Group G, R 2 is aryl, a monocyclic aromatic hetero ring, or a bicyclic aromatic hetero ring, which each may be substituted with 1 to 5 substituents selected from the Group G, R 3 's are the same as or different from each other, and are each C 1-6 alkyl, W is C 1-6 alkylene, and n is an integer of 0 to 4), wherein the Group G is the group consisting of: (a) C 1-6 alkyl which may be substituted with at least one group selected from the group consisting of -OH, -O-(C 1-6 alkyl), -CN, -SO 2 -(C 1-6 alkyl), and halogen, (b) -OH, (c) -O-(C 1-6 alkyl which may be substituted with at least one group selected from the group consisting of -OH, -O-(C 1-6 alkyl), -CN, -SO 2 -(C 1-6 alkyl), and halogen), (d) C 3-8 cycloalkyl, (e) -O-(C 3-8 cycloalkyl), (f) halogen, (g) -CN, (h) -SO 2 -(C 1-6 alkyl), (i) -CO 2 -(C 1-6 alkyl) and -COOH, (j) -CO-N(C 1-6 alkyl) 2, -CO-NH(C 1-6 alkyl), and -CONH 2, (k) -CO-(C 1-6 alkyl), (l) -SO 2 -N(C 1-6 alkyl) 2, -SO 2 -NH(C 1-6 alkyl), and -SO 2 NH 2, (m) -N(C 1-6 alkyl) 2, -NH(C 1-6 alkyl), and -NH 2, (n) saturated hetero ring, and (o) -O-saturated hetero ring. R 1 is -N(-R 11)(-R 12), or cyclic amino which may be substituted with 1 to 5 substituents selected from the group consisting of Group G and oxo, R 11 is C 1-6 alkyl, R 12 is C 1-6 alkyl which may be substituted with 1 to 5 substituents selected from substituents (b) to (o) of the Group G, or C 3-8 cycloalkyl which may be substituted with 1 to 5 substituents selected from the Group G, R 2 is aryl, a monocyclic aromatic hetero ring, or a bicyclic aromatic hetero ring, which each may be substituted with 1 to 5 substituents selected from the Group G, R 3 's are the same as or different from each other, and are each C 1-6 alkyl, W is C 1-6 alkylene, and n is an integer of 0 to 4), wherein the Group G is the group consisting of: (a) C 1-6 alkyl which may be substituted with at least one group selected from the group consisting of -OH, -O-(C 1-6 alkyl), -CN, -SO 2 -(C 1-6 alkyl), and halogen, (b) -OH, (c) -O-(C 1-6 alkyl which may be substituted with at least one group selected from the group consisting of -OH, -O-(C 1-6 alkyl), -CN, -SO 2 -(C 1-6 alkyl), and halogen), (d) C 3-8 cycloalkyl, (e) -O-(C 3-8 cycloalkyl), (f) halogen, (g) -CN, (h) -SO 2 -(C 1-6 alkyl), (i) -CO 2 -(C 1-6 alkyl) and -COOH, (j) -CO-N(C 1-6 alkyl) 2, -CO-NH(C 1-6 alkyl), and -CONH 2, (k) -CO-(C 1-6 alkyl), (l) -SO 2 -N(C 1-6 alkyl) 2, -SO 2 -NH(C 1-6 alkyl), and -SO 2 NH 2, (m) -N(C 1-6 alkyl) 2, -NH(C 1-6 alkyl), and -NH 2, (n) saturated hetero ring, and (o) -O-saturated hetero ring. (a) C 1-6 alkyl which may be substituted with at least one group selected from the group consisting of -OH, -O-(C 1-6 alkyl), -CN, -SO 2 -(C 1-6 alkyl), and halogen, (b) -OH, (c) -O-(C 1-6 alkyl which may be substituted with at least one group selected from the group consisting of -OH, -O-(C 1-6 alkyl), -CN, -SO 2 -(C 1-6 alkyl), and halogen), (d) C 3-8 cycloalkyl, (e) -O-(C 3-8 cycloalkyl), (f) halogen, (g) -CN, (h) -SO 2 -(C 1-6 alkyl), (i) -CO 2 -(C 1-6 alkyl) and -COOH, (j) -CO-N(C 1-6 alkyl) 2, -CO-NH(C 1-6 alkyl), and -CONH 2, (k) -CO-(C 1-6 alkyl), (l) -SO 2 -N(C 1-6 alkyl) 2, -SO 2 -NH(C 1-6 alkyl), and -SO 2 NH 2, (m) -N(C 1-6 alkyl) 2, -NH(C 1-6 alkyl), and -NH 2, (n) saturated hetero ring, and (o) -O-saturated hetero ring.