h,w=map(int,input().split())
S=[list(input()) for _ in range(h)]

if sum(row.count('#') for row in S)==0:
    print('NO')
    exit()
    
for di in range(-h,h):
    for dj in range(-w,w):
        if di==0 and dj==0:continue
        
        ok=True
        mass=[row[:] for row in S]
        for i in range(h):
            for j in range(w):
                if mass[i][j]!='#':continue
                mass[i][j]='R'
                ni,nj=i+di,j+dj
                if 0<=ni<h and 0<=nj<w and mass[ni][nj]=='#':
                    mass[ni][nj]='B'
                else:
                    ok=False
                    break
                
            if not ok:break
        
        if ok:
            print('YES')
            exit()

print('NO')