while True:
     (H, W) = [int(x) for x in input().split()]
     if H == Q == 0:
         break
    
     for hc in range(H):
            for wc in range(W):
                  if (hc + wc) % 2 == 0:
                       print('#', end='')
                  else:
                       print('.',end='')
            print()
     print()