import Foundation

// Start of `Node` class
class Node {
    var value: Int
    var left: Node?
    var right: Node?

    init(_ value : Int) {
        self.value  = value
    }
    
    func insert(_ value: Int) {
        if value < self.value {
            if let left {
                left.insert(value)
            } else {
                left = Node(value)    
            }
        } else if value > self.value {
            if let right {
                right.insert(value)
            } else {
                right = Node(value)
            }
        }
    }
    
    // Start of `lowestCommonAncestor` method
    func lowestCommonAncestor(_ node1: Int, _ node2: Int) -> Int? {
        
        // Enter your code here

    } // End of `lowestCommonAncestor` method
}

// Start of `Tree` class
class Tree {
    var root: Node?
    
    func insert(_ value: Int) {
        if let root {
            root.insert(value)
        } else {
            root = Node(value)
        }
    }
} // End of `Tree` class

let tree = Tree()

guard let _ = readLine(), // first line not needed
    let treeNodes = readLine()?.split(separator: " ").compactMap({ Int($0) }),
    let inputNodes = readLine()?.split(separator: " ").compactMap({ Int($0) }),
    inputNodes.count == 2
else {
    print("ERROR: Invalid Input!")
    exit(-1)
}

treeNodes.forEach { node in
    tree.insert(node)
}

// Result:
if let result = tree.root?.lowestCommonAncestor(inputNodes[0], inputNodes[1]) {
    print(result)
} else {
    print("No LCA!")
}