#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 *inOrder(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);
    }
    inOrder(root);
    return 0;
}