H,W=map(int,input().split())
S=[input() for _ in range(H)]

Flag=0
for y in range(0,H+1):
    for x in range(-(W-1),W):
        if x==y==0:
            continue

        T=[[int(S[y][x]=="#") for x in range(W)] for y in range(H)]
        G=1
        K=0

        for b in range(H):
            for a in range(W):
                if T[b][a]:
                    if 0<=b+y<H and 0<=a+x<W and T[b+y][a+x]:
                        T[b][a]=T[b+y][a+x]=0
                        K=1
                    else:
                        G=0
        Flag|=G&K

if Flag:
    print("YES")
else:
    print("NO")