while 1:
   H, W = map(int, raw_input().split())
            
   if H == 0 and W == 0:
      break
   for i in range(0, H):
      if i%2 == 0:
         if W%2 == 0:
            print "#."*(W/2)
         else:
            print "#."*(w/2)+"#"
      else:
         if W%2 == 0:
            print ".#"*(W/2)
         else:
            print ".#"*(w/2)+"."
   print ""