// editor2
#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    char 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,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->rigt,num);
    return root;    
    }  
}
void inorder(Node *root){
    if(root!=NULL){
        inorder(root->left);
        printf("%d ",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);
        inordder(root);
        return 0;

}