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