#include<stdio.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(1*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);
    }
    return root;
}
void inOrder(node *root){
    if(root!=NULL){
        inOrder(root->left);
        printf("%c ",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);
    }
        getchar();
        root = insert(root,num);
    }
    inOrder(root);
    return 0;
}