while True:
    h,w = map(int,input().split())
    if h ==0 and w==0:
        break
    else:
        for i in range(h):
            if i%2 ==0:
                for j in range(w):
                    if j%2 ==0:
                        print('#',end='')
                    else:
                        print('.',end='')
            else:
                for j in range(w):
                    if j%2 ==0:
                        print('.',end='')
                    else:
                        print('#',end='')
            print('')
