// editor1
#include<stdio.h>
#include<stdlib.h>
typedef struct treenode{
    int data;
    struct treenode *right;
    struct treenode *left;
    struct treenode *
} node;
node *root =NULL;
node *create(int num){
    node *newnode = (node*)malloc(sizeof(node));
    newnode->data=num;
    newnode->left=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
    root->right =insert(root->right,num);
    return root;
}
void level(node *root){
    if(root == NULL){
        return;
    }
    node *queue[100];
    int front = 0 ,rear = 0;
    queue[rear++] = root;
    while(front<rear){
        node curr = queue[front++];
        printf("%d",curr->data);
        if(curr->left){
            queue[rear++]=curr->left;
        }
        if(curr->right){
            queue[rear++]=curr->right;
        }
        
    }
    
    
}
int main(){
    int num,size;
    scanf("%d",&size);
    if(size<=0){
        printf("Invalid input");
        return 0;
    }
    for(int i = 0;i<size;i++){
    scanf("%d",&num);
    root =insert(root,num);
}
//insert(root,num);
level(root);
return 0;
}