#include <iostream>
using namespace std;
struct bnode {
	int data;
	struct bnode *l,*r;
	bnode(int data)
	{
		this->data = data;
		l = r = NULL;
	}
};
void getparent(struct bnode *T,int x,int &p){
    if(T==NULL) return;
    if(T->l!=NULL and T->l->data==x){
        p=T->data;
        return ;
    }
    if(T->r!=NULL and T->r->data==x){
        p=T->data;
        return ;
    }
    getparent(T->l,x,p);
    getparent(T->r,x,p);
}
bnode* get_sibling(bnode *node, int key)
{
    if (node == NULL || node->data == key)
    {
      return NULL;
    }

    if (node->l != NULL && node->l->data == key)
    {
      return node->r;
    }

    if (node->r != NULL && node->r->data == key)
    {
      return node->l;
    }

    bnode *temp = get_sibling(node->l, key);

    if (temp != NULL)
    {
      return temp;
    }

    temp = get_sibling(node->r, key);
    return temp;
}


int main()
{

	struct bnode* root = new bnode(4);
	root->l = new bnode(3);
	root->r = new bnode(9);
	root->l->l = new bnode(5);
	root->l->r = new bnode(6);
	root->r->l = new bnode(1);
	root->r->r = new bnode(8);
	int node,p;
	cout<<"enter node value : "<<endl;
	cin>>node;
    getparent(root,node,p);
    bnode *sibling = get_sibling(root,p);
    if (sibling != NULL)
    {
        cout<<"The uncle of "<<node<<" is " << sibling->data<<endl;
    } else {
        cout<<-1<<endl;
    }

	return 0;
}