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

D = [list(input()) for h in range(H)]

count = sum(D[h].count("#") for h in range(H))

if count == 0 or count % 2 == 1:
    print("NO")
    exit()

for h in range(H):
    for w in range(W):


        for i in range(H-h):
            for j in range(-w, W-w):
                if D[h][w] == "#" and D[h+i][w+j] == "#":
                    D[h][w], D[h+i][w+j] = ".", "."

count = sum(D[h].count("#") for h in range(H))

if count == 0:
    print("YES")
else:                    
    print("NO")