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

S = [[1 if i == '#' else 0 for i in input()] for _ in range(H)]

from copy import deepcopy

if sum([sum(s) for s in S]) < 2:
    
    print('NO')
    
    exit()

for i in range(H):
    
    for j in range(-W + 1, W):
        
        if i == 0 and j <= 0:
            
            
            continue
        
        
        else:
            
            s = deepcopy(S)
            
            B = True
            
            for h in range(H):
                
                if B:
                    
                    
                    for w in range(W):
                    
                      if s[h][w] == 1:
                          
                          s[h][w] = 0
                          
                          if h + i < H and 0 <= w + j < W and s[h + i][w + j]:
                              
                              s[h + i][w + j] = 0
                              
                              
                          else:
                              
                              B = False
                              
                              break
                          
                          
                else:
                    
                    break
                
            if B:
                
                print('YES')
                
                exit()
                
                
                
print('NO')