traverse() : (A1) => Node(1000, 4000)
traverse() : (B1) => Node(12000, 18500)
traverse() : (A2) => Node(15000, 22000)
traverse() : (B2) => Node(28000, 29000)
traverse() : (A3) => Node(30000, 32000)
traverse() : (A4) => Node(42000, 44000)