// editor2
#include<stdio.h>
#include<stdlib.h>
struct Node
{
    int data;
    struct Node*next;
};
int main()
{
    int n,i,value;
    scanf("%d",&n);
    if(n<=0){
        printf("Invalid input");
        return 0;
    }
    struct Node*head=NULL,**temp=NULL,*newNode;
    for(i=0;i<n;i++){
        scanf("%d",&value);
           
           if(value<0){
            printf("Invalid input");
            return 0;
        }
        newNode=(struct Node*)malloc(sizeof(struct Node));
        newNode->data=value;
        newNode->next=NULL;
        if(head==NULL){
            head=newNode;
            temp=newNode;
        }
    }
    temp=head;
    while(temp!=NULL){
        printf("%d",temp->data);
        temp=temp->next;
    }
    return 0;
}