#include <iostream>
using namespace std;
struct tree{
  int oznaka;
  tree *left, *right;
};
tree *root;
void Init(int broj){
  root=new tree;
  root->oznaka=broj;
  root->left=0;
  root->right=0;
}
tree* LeftChild(tree* cvor){
  if(cvor) return cvor->left;
  return 0;
}
tree* RightChild(tree* cvor){
  if(cvor) return cvor->right;
  return 0;
}
int Label(tree *cvor){
  return cvor->oznaka;
}
void ChangeLabel(int a, tree *cvor){
  cvor->oznaka=a;
}
tree* Root(){
  return root;
}
tree* Parent(tree* dijete, tree* cvor=root){
  if(!cvor) return 0;
  if(cvor->left==dijete||cvor->right==dijete) return cvor;
  Parent(dijete, cvor->left);
  Parent(dijete, cvor->right);
}
void Delete(tree *cvor){
  tree *roditelj=Parent(cvor);
  if(roditelj->left==cvor) roditelj->left=0;
  if(roditelj->right==cvor) roditelj->right=0;
  if(cvor->left) Delete(cvor->left);
  if(cvor->right) Delete(cvor->right);
  delete cvor;
}
void CreateLeft(int broj, tree *cvor){
  if(cvor->left) cout<<"Error!"<<endl;
  tree *novi=new tree;
  cvor->left=novi;
  novi->left=0;
  novi->right=0;
  novi->oznaka=broj;
}
void CreateRight(int broj, tree *cvor){
  if(cvor->right) cout<<"Error!"<<endl;
  tree *novi=new tree;
  cvor->right=novi;
  novi->left=0;
  novi->right=0;
  novi->oznaka=broj;
}