H,W=map(int,input().split())
s=[list(input()) for i in range (H)] 
import sys
for j in range (1,W):
    for k in range (1,H-1):
        if s[j][k]=='#' and s[j][k-1]=='.' and s[j][k+1]=='.' and s[j-1][k]=='.' and s[j+1][k]=='.':
            print ('No')
            sys.exit()