import sys
while 1:
  H, W = map(int, raw_input().split())
  if H == 0 and W == 0:
    break
  else:
    for h in range(H):
      for w in range(W):
         if (h + w) % 2 == 0:
           sys.stdout.write("#")
         else:
           sys.stdout.write(".")
      print ""
    print ""
 
  