#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define LINE_MAX 1000

int comp( const void *p1, const void *p2 )
{
	return strcmp( *(char **)p1, *(char **)p2 );
}

main()
{
	char buf[BUFSIZ];
	char *line[LINE_MAX];
	char *p;
	int i, n;

	for (i = 0; fgets(buf, sizeof buf, stdin) != NULL && i < LINE_MAX; i++) {
		p = (char *)malloc( sizeof(char) * (strlen(buf)+1));
		strcpy(p, buf);
		line[i] = p;
	}
	n = i;

	qsort( line, n, sizeof line[0], comp );

	for (i = 0; i < n; i++)
		printf("%s", line[i]);

	exit(0);
}