public class Solution {
    public static class Node{
        int data;
        Node left,right;
    }

    public static Node construct(int arr[],int lo,int hi){
        if(lo > hi){
            return null;
        }
        int mid = (lo+hi)/2;
        Node node = new Node();
        node.data = arr[mid];

        node.left = construct(arr, lo, mid-1);
        node.right = construct(arr, mid+1 , hi);

        return node;
    }

    public static void display(Node node){
        if(node == null){
            return;
        }
        System.out.print(node.left == null ? "." : node.left.data);
        System.out.print(" <- "+node.data+" -> ");
        System.out.println(node.right == null ? "." : node.right.data);

        display(node.left);
        display(node.right);
    }
    public static void main(String[] args) {
        int arr[] = {10,20,30,40,50,60,70}; // sorted integers

        Node root = construct(arr, 0, arr.length-1);
        display(root);
    }
}