#include<stdio.h>
#include<stdlib.h>
typedef struct node {
    int data;
    struct node *left,*right;
}Node;
Node *create(int num) {
     Node *newnode=(Node*)malloc(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->right=insert(root->right);
    else if(num<root->data)
    root->left=insert(root->left)
    return root;
}
void inorder(Node *root) {
    if(root!=NULL) {
        inorder(root->left,num);
        printf("%c",root->data);
        inorder(root->right,num);
    }
}
int main() {
    int size,num,itr;
    scanf("%d",&size);
    if(size<0) {
        printf("Invalid input");
        return 0;
    }
    getchar();
    for(itr=0;itr<size*2;itr++) {
        if(root==' ')
        {
            continue;
        }
        scanf("%c",&num);
        root=insert(root,num);
    }
    inorder(root);
    return 0;
    
}