"""

https://yukicoder.me/problems/no/179

ずらし方全探索

"""

class DSU():

    def __init__(self, n:int):

        self.n = n
        self.p = [i for i in range(n)]
        self.rank = [i for i in range(n)]
        self.sizelis = [1] * n

    def leader(self,a):
        stk = []
        while self.p[a] != a:
            stk.append(a)
            a = self.p[a]
        for v in stk:
            self.p[v] = a
        return a

    def merge(self, a, b):
        ap = self.leader(a)
        bp = self.leader(b)
        if ap == bp:
            return ap

        if self.rank[ap] > self.rank[bp]:
            self.p[bp] = ap
            self.sizelis[ap] += self.sizelis[bp]
        elif self.rank[ap] < self.rank[bp]:
            self.p[ap] = bp
            self.sizelis[bp] += self.sizelis[ap]
        else:
            self.p[bp] = ap
            self.sizelis[ap] += self.sizelis[bp]
            self.rank[ap] += 1
        return self.p[ap]

    def same(self,a,b):
        return self.leader(a) == self.leader(b)

    def size(self,a):
        return self.sizelis[ self.leader(a) ]

    def groups(self):
        dic = {}
        for v in range(self.n):
            vp = self.leader(v)
            if vp not in dic:
                dic[vp] = [v]
            else:
                dic[vp].append(v)
        return list(dic.values())

import sys

def check(dx,dy):

    uf = DSU(H*W)
    
    for i in range(H):
        for j in range(W):

            if S[i][j] == ".":
                continue

            cnt = 0

            if 0 <= i+dx < H and 0 <= j+dy < W and S[i+dx][j+dy] == "#":
                uf.merge( i*W+j , (i+dx)*W+j+dy )
            if 0 <= i-dx < H and 0 <= j-dy < W and S[i-dx][j-dy] == "#":
                uf.merge( i*W+j , (i-dx)*W+j-dy )

    for i in range(H):
        for j in range(W):
            if S[i][j] == "#" and uf.size(i*W+j)%2==1:
                return False

    return True
            

H,W = map(int,input().split())

S = [ input() for i in range(H) ]

for dx in range(-50,51):

    for dy in range(-50,51):

        if check(dx,dy):
            print ("YES")
            sys.exit()

print ("NO")