// yukicoder: No.179 塗り分け
// 2019.6.24 bal4u

#include <stdio.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() {   // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

void ins(char *s)  // 文字列の入力　スペース以下の文字で入力終了
{
	do *s = gc();
	while (*s++ > ' ');
	*(s-1) = 0;
}

int H, W, N;
char S[105][105];
int t[105][105]; 
int maxr, maxc;

int check(int h, int w) {
	int r, c, id, n;
	id = ((w + 64) << 8) | h, n = 0;
	for (r = 0; r <= maxr; r++) for (c = 0; c <= maxc; c++) {
		if (S[r][c] == '#' && t[r][c] != id) {
			if (r+h < 0) return 0;
			if (S[r+h][c+w] != '#') return 0;
			t[r+h][c+w] = id;
			if (++n == N) return 1;
		}
	}
	return 0;
}
		
int main()
{
	int r, c;

	H = in(), W = in();
	N = 0, maxr = maxc = 0;
	for (r = 0; r < H; r++) {
		ins(S[r]);
		for (c = 0; c < W; c++) if (S[r][c] == '#') {
			if (c > maxc) maxc = c;
			maxr = r;
			N++;
		}
	}
	if (N == 0 || (N & 1)) goto NO;
	if (N == H*W) goto YES;
	N >>= 1;
	for (r = 0; r <= maxr; r++) for (c = -maxc; c <= maxc; c++) {
		if (c == 0 && r == 0) continue;
		if (check(r, c)) goto YES;
	}
NO:	puts("NO");
	return 0;
YES:puts("YES");
	return 0;
}