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")