# -*- coding: utf-8

while True:
   a = list(map(int,input().split()))
   if a == [0,0]:
      break
   if a[1] % 2 == 0:
      b1 = "#."*int(a[1]/2)
      b2 = ".#"*int(a[1]/2)
   if a[1] % 2 == 1:
      b1 = "#."*int((a[1]-1)/2)+"#"
      b2 = ".#"*int((a[1]-1)/2)+"."
   
   if a[0] %2 == 0:
      for i in range(a[0]/2):
         print(b1)
         print(b2)
   if a[0] %2 == 1:
      for i in range((a[0]-1)/2):
         print(b1)
         print(b2)
      print(b1)
   print("")

