#include<stdio.h>
#include<ctype.h>
#include<stdlib.h>
typedef struct node{
    char data;
    struct node*left,*right;
}Node;
Node *create(char ch){
    Node *newnode =(Node*)malloc(sizeof(Node));
    strcpy(newnode->data,ch);
    newnode->left=NULL;
    newnode->right=NULL;
    return newnode;
}
Node *insert(Node *root,char ch){
    if(root==NULL)
    return create(ch)
    if(<root->data)
    root->left=insert(root->left,num);
    if(>root->data)
    root->right=insert(root->right,num);
    return root;
}

void inorder(Node *root){
    inorder(root->left);
    printf("%c",root->data);
    inorder(root->right);
}
int main(){
    int n,i,num;
    scanf("%d",&n);
    if(n<=0){
        printf("Invalid input");
        return 0;
    }
    getchar();
    for(i=0;i<n*2;i++){
        scanf("%c",num)
        if(num=' ')
        continue;
        root=insert(root,num);
    }
    inorder(root);
}