[Problems to be Solved by the Invention]To provide a drug having excellent antibacterial activity against Gram-positive bacteria and Gram-negative bacteria and also being excellent in terms of safety.[Means for Solving the Problems]A compound represented by the following formula (I) or a salt thereof:wherein R represents a hydrogen atom, a hydroxy group, or a halogen atomm represents an integer 0, 1, or 2,n represents an integer 0 or 1Ar1 represents a bicyclic heterocyclic group represented by the following formula:wherein Aa represents a nitrogen atom or C-Ra, Ab represents a nitrogen atom or C-Rb, and Ac represents a nitrogen atom or C-Rc, Ra, Rb, and Rc independently represent a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms,R1 and R2 independently represent a hydrogen atom, an alkoxy group containing 1 to 6 carbon atoms, a halogenoalkoxy group containing 1 to 6 carbon atoms, a halogen atom, or a cyano group,Ar2 represents a bicyclic heterocyclic group represented by the following formulae:
