#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    int data;
    struct node*left;
    struct node*right;
}a;
a* root=NULL;
a* create(int num){
    a*newnode=(a*)malloc(1*sizeof(a));
    newnode->data=num;
    newnode->left=NULL;
    newnode->right=NULL;
    return newnode;
}
a* insert(a* 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(a*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=='\n'){
            continue;
        }
        root=insert(root,num);
    }inorder(root);
return 0;
}