#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define INIT (Tree *)malloc(sizeof(Tree))
int n;
char inf[100][100];
typedef struct node
{
	char ch;
	struct node *l, *r;
}Tree;

Tree *root;

int input()
{
	char tmp[100];

	n = -1;
	while(scanf("%s",tmp)==1)
	{
		if(tmp[0]=='*')
			break;
		if(tmp[0]=='$')
			return 0;
		strcpy(inf[++n],tmp);
	}
	return 1;
}

void insert(char ch)
{
	Tree *s, *p;

	s = root;
	p = INIT;
	p->ch = ch;
	p->l = p->r = NULL;
	while(s)
	{
		if(ch>s->ch)
			if(s->r)
				s = s->r;
			else
			{
				s->r = p;
				break;
			}
		else
			if(s->l)
				s = s->l;
			else
			{
				s->l = p;
				break;
			}
	}
}

void visit(Tree *a)
{
	printf("%c",a->ch);
	if(a->l)
		visit(a->l);
	if(a->r)
		visit(a->r);
}

int solve(int com)
{
	int i, j;

	root = INIT;
	root->ch = inf[n][0];
	root->l = root->r = NULL;
	for(i = n-1; i >= 0; i--)
	{
		for(j = 0; inf[i][j]!='\0'; j++)
			insert(inf[i][j]);
	}
	visit(root);
	printf("\n");
	return com;
}

int main()
{
	while(solve(input()));
	return 1;
}