// editor2
#include <stdio.h>
#include <stdlib.h>
typedef struct node{
    int data;
    struct node *left,*right;
}Node;

Node *root=NULL;
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->left=insert(root->left,num);
    else if(num>root->data)
        root->right=insert(root->right,num);
    return root;
}

void inorder(Node *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=0;itr<=size;itr++){
        scanf("%c",&num);
        if(num==' ')
        continue;
        root=insert(root,num);
        
    }
    inorder(root);
    return 0;
}