h,w = map(int, input().split())
l = []
for _ in range(h):
    l.append(input())

x = [1,0,-1,0]
y = [0,1,0,-1]

flag = False

#normal
for i in range(1,h-1):
    for j in range(1,w-1):
        if(l[i][j] == '#'):
            for k in range(4):
                if(l[i + x[k]][j + y[k]] == '#'):
                    flag = True
                    break
            else:
                continue
            break

#tate



if(flag == True):
    print('Yes')
else:
    print('No')

