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

#define N 50

char s[N*N+1], ss[N*N+1];

int main() {
  int h, w, i, j, dh;

  scanf("%d %d", &h, &w);
  for (i = 0; i < h; i++) {
    scanf("%s", s+i*w);
  }
  if (strchr(s, '#') != NULL) {
    strcpy(ss, s);
    for (i = 1; s[i] != '\0'; i++) {
      dh = -1;
      for (j = 0; s[i+j] != '\0'; j++) {
        if (s[j] != '#') continue;
        if (dh < 0) dh = (i+j)/w - j/w;
        s[j] = 'R';
        if ((i+j)/w - j/w != dh) break;
        if (s[i+j] != '#') break;
        s[i+j] = 'B';
      }
      if (strchr(s, '#') == NULL) {
        puts("YES\n");
        return 0;
      }
      strcpy(s, ss);
    }
  }
  puts("NO\n");

  return 0;
}