n = "#."
m = ".#"
 
while 1:
   H, W = map(int, raw_input().split())
 
   if H == 0 and W == 0:
      break
   if W%2 ==0:
      for i in range(0, H, 2):
         M[i] = n*(w/2)
      for i in range(1, H, 2):
         M[i] = m*(W/2)
   elif W%2 == 1:
      for i in range(0, H, 2):
         M[i] = n*(w/2)+n(0)
      for i in range(1, H, 2):
         M[i] = m*(W/2)+m(0)
 
   for i in range(H):
      print "%c" %(M[i])
   print ""