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