odd = ['#','.']
even = ['.','#']
while True:
    h,w = map(int, raw_input().split())
    if h == w == 0:
        break 
    ret = []
    for i in range(h):
        ret += [odd[j%2] if i % 2 == 0 else even[j%2] for j in range(w)]
        ret += ['\n']
    print(''.join(ret))