// editor2// editor3
#include<stdio.h>
#include<stdlib.h>

typedef struct node{
    int data;
    struct node*left,*right;
}node;

node *root=NULL;

node *create(char num){
    node *newnode=(node*)malloc(1*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);
    }else if(num<root ->data){
        root->left=insert(root->left,num);
    }else if(num>root->data){
        root->right=insert(root->right,num);
    }
    return root;
}

node *intorder(node *root){
    if(root!=NULL){
        inorder(root->left);
                printf("%c ",root->data);
        inorder(root->right);
    }
}
int main(){
    int size,itr;
    char ch;
    scanf("%d",&size);
    if(size<0){
        printf("Invalid input");
        return 0;
    }
    for(itr=0;itr<=size*2;itr++){
        scanf("%c",&ch);
        root=insert(root,ch);
    }
    intorder(root);
    return 0;
}