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

char pole[31][33];
struct limit {
	unsigned char maxx,minx,maxy,miny;
} limit['Z'-'A'+1], *lptr;
char znaky[30];

char res[5000][30];
int h,w, rcount;

int ontop(const char c) {
	int i;
	struct limit *l=&limit[c-'A'];
	for (i=l->minx; i<=l->maxx; ++i)
		if ( ((pole[l->miny][i] != c) && (pole[l->miny][i] != '*'))
			||
			((pole[l->maxy][i] != c) && (pole[l->maxy][i] != '*'))
		   )
				return 0;
	for (i=l->miny; i<=l->maxy; ++i)
		if ( ((pole[i][l->minx] != c) && (pole[i][l->minx] != '*'))
			||
			((pole[i][l->maxx] != c) && (pole[i][l->maxx] != '*'))
		   )
				return 0;
	return 1;
}

void replace(const char c, const char to) {
	int i;
	struct limit *l=&limit[c-'A'];
	for (i=l->minx; i<=l->maxx; ++i) {
		pole[l->miny][i] = to;
		pole[l->maxy][i] = to;
	}
	for (i=l->miny; i<=l->maxy; ++i) {
		pole[i][l->minx] = to;
		pole[i][l->maxx] = to;
	}
}

void find(char *zbyvajici, char *nalezene) {
	int i;
	char *s;
	for (s=zbyvajici; *s; ++s)
		if (ontop(*s)) {
			char zb[30] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
			char str[30] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
			char *p1,*p2, backup[31][33];
			strcpy(str,nalezene);
			str[strlen(str)] = *s;
			for (p1=zbyvajici,p2=zb; *p1; ++p1)
				if (*p1 != *s)
					*p2++ = *p1;
			if (!*zb) {
				res[rcount][i=strlen(s=str)] = '\0';
				while (i)
					res[rcount][--i] = *s++;
				rcount++;
				return;
			}
/*			printf("found %c\nfind('%s', '%s')\n", *s, zb,str);*/
			memcpy(backup, pole, sizeof(backup));
			replace(*s, '*');
/*			for(i=0; i<h; ++i)
				printf("%s", pole[i]);*/
			find(zb, str);
			memcpy(pole, backup, sizeof(backup));
		}
}

int main() {
	int i,zcount;
	int x,y;
	char c, znaky[30];
	for(;;) {
		scanf("%d\n%d\n", &h,&w);
		if (!h && !w)
			return 0;
		for(i=0; i<h; ++i)
			fgets(pole[i], 33, stdin);
		/* get limits */
		memset(limit, 99, sizeof(limit));
		memset(znaky,'\0',sizeof(znaky));
		for (y=0; y<h; ++y)
			for (x=0; x<w; ++x) {
					if ((c=pole[y][x]) != '.') {
						if (!strchr(znaky,c))
							znaky[strlen(znaky)] = c;
						lptr = &limit[c-'A'];
						if (x < lptr->minx)
							lptr->minx = x;
						if (y < lptr->miny)
							lptr->miny = y;
						if ((x > lptr->maxx) || (lptr->maxx == 99))
							lptr->maxx = x;
						if ((x > lptr->maxy) || (lptr->maxy == 99))
							lptr->maxy = y;
					}
				}
		rcount=0;
		for (i=0; i<=('Z'-'A'); ++i)
			if (znaky[i]) zcount++;
		find(znaky, "");

		if (rcount > 1) {
			int comp(const void* a,const void *b) {return strcmp(a,b);}
			qsort(res, rcount, 30, comp);
		}

		for (i=0; i<rcount; ++i)
			printf("%s\n", res[i]);
		printf("\n");
	}
	return 0;
}