#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 *ins(node *root,char num){
    if(root==NULL){
        return create(num);
    }
    if(num<root->data){
        root->left=ins(root->left,num);
    }
    else if(num>root->data){
        root->right=ins(root->right,num);
    }
    return root;
}

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