// 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(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("%c",&num);
    if(num=='  '){
        continue;
    }
    root=insert(root,num);
}
inorder(root);
return 0;
}