while True:  

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

  elif i%2==1:
   if W%2==0:
    print ".#"*(W/2)
   elif W%2==1:
    print ".#"*(W/2)+"."
 print ""