#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    char data;
    struct node *right,*left;
}Node;
Node*root=NULL;
Node *create(char num)
{
    Node *newnode=(Node*)malloc(sizeof(Node));
    newnode->data=num;
    newnode->right=NULL;
    newnode->left=NULL;
    return newnode;
}
Node *insert(Node*root, char num)
{
    if(root==NULL)
      return create(num);
    if(num<root->data)
      root->left=insert(root->left);
    if(num>root->data)
      root->right=insert(root->right);
      return root;
}
void inorder(Node *root)
{
    inorder(root->left);
    printf("%c",root->data);
    inoder(root->right);
}
int main()
{
    int n,i;
    char num;
    if(n<0)
    {
        printf("Invalid input");
        return 0;
    }
    getchar();
    for(i=1;i<n*2;i++)
    {
        if(num==' ')
         continue;
         root =insert(root,num);
    }
    inorder(root);
}