for i in range(10000):
  x = input().split()
  h = int(x[0])
  w = int(x[1])
  if h == 0 and w == 0:
    break
    
  if h % 2 == 0:
    
    if w % 2 == 0:
      for i in range(h):
        for i in range(w//2):
          print("#",end="")
          print(".",end="")
        print()
        for i in range(w//2):
          print(".",end="")
          print("#",end="")
        print()
      print()
      
    elif w % 2 == 1:
      for i in range(h):
        for i in range((w-1)//2):
          print("#",end="")
          print(".",end="")
        print("#",end="")  
        print()
        for i in range((w-1)//2):
          print(".",end="")
          print("#",end="")
        print(".",end="")  
        print()  
      print()
      
  
  elif h % 2 == 1:
    
    if w % 2 == 0:
      for i in range((h-1)//2):
        for i in range(w//2):
          print("#",end="")
          print(".",end="")
        print()
        for i in range(w//2):
          print(".",end="")
          print("#",end="")
        print()
      for i in range(w//2):
        print("#",end="")
        print(".",end="")
      print()
      print()
      
    elif w % 2 == 1:
      for i in range((h-1)//2):
        for i in range((w-1)//2):
          print("#",end="")
          print(".",end="")
        print("#",end="")  
        print()
        for i in range((w-1)//2):
          print(".",end="")
          print("#",end="")
        print(".",end="")  
        print()  
      for i in range((w-1)//2):
        print("#",end="")
        print(".",end="")
      print("#",end="")  
      print()
          
