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