#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    int data;
    struct node *next;
    struct node *prev;
}Node;
Node *head=NULL, *tail;
void create(int num){
    Node *newnode=(Node*)malloc(1*sizeof(Node));
    newnode->data=num;
    newnode->next=NULL;
    newnode->prev=NULL;
    if(head==NULL){
        head=newnode;
        tail=newnode;
    }
    else{
        newnode->prev=tail;
        tail->next=newnode;
        tail=newnode;
    }
}
void display(){
    Node *itr;
    for(itr=head;itr!=NULL;itr=itr->next){
        printf("%d",itr->data);
    }
}
int main(){
    int i,num,size;
    scanf("%d",&num);
    if(size<=0){
        printf("Invalid input");
        return 0;
    }
    for(i=0;i<size;i++){
        if(!(scanf("%d",&num))){
            printf("Invalid input");
            return 0;
        }
    create(num);
    }
    display();
    return 0;
    }
}