#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
struct node
{
	char data[101];
	struct node *next;
};
int main()
{
	int n,i;
	struct node*start=NULL;
	struct node*temp=NULL;
	struct node*currend=NULL;
	scanf("%d",&n);
	start=(struct node*)malloc(sizeof(struct node));
	scanf("%s",start->data);
	start->next=NULL;
	currend=start;
	
	for(i=2;i<=n;i++)
	{
	    temp=(struct node*)malloc(sizeof(struct node));
	    scanf("%s",temp->data);
	    start->next=NULL;
	    currend->next=temp;
	    currend=temp;
	}
	currend=start;
	while(currend!=NULL)
	{
	    for(i=0;currend->data;[i]='\0';i++)
	    {
	        if(!isalnum(currend->data[i]))
	        {
	            printf("Invalid input");
	            return 0;
	        }
	    }
	    currend=currend->next;
	}
	currend=start;
	while(currend!=NULL)
	{
	    printf("%s",currend->data);
	    currend=currend->next;
	}
	return 0;
}