#include <stdio.h>

int main(int argc, char *argv[]) {
  for (;;) {
    int w, h, i, j;
    scanf("%d", &w), scanf("%d", &h);
    if (w == 0 && h == 0) return 0;
    char c[w + 1];
    int dlen[w], dmaxlen;
    char d[w][w + h + 1], dmax[w + h + 1];
    for (i = 0; i < w; i++) dlen[i] = 0;
    dmaxlen = 0;
    for (j = 0; j < h; j++) {
      scanf("%s", c);
      for (i = 0; i < w; i++) {
	if (!isdigit(c[i])) {
	  dlen[i] = 0;
	  continue;
	}
	if (i && (dlen[i-1] > dlen[i] || (dlen[i-1] == dlen[i] && memcmp(d[i-1], d[i], dlen[i]) > 0)))  memcpy(d[i], d[i - 1], dlen[i] = dlen[i - 1]);
	if (d[i][0] == '0') dlen[i] = 0;
	d[i][dlen[i]++] = c[i];
	if (dlen[i] > dmaxlen || (dlen[i] == dmaxlen && memcmp(d[i], dmax, dmaxlen) > 0)) memcpy(dmax, d[i], dmaxlen = dlen[i]);
      }
    }
    dmax[dmaxlen] = '\0';
    printf("%s\n", dmax);
  }
}