x = []
s = ['','']
while True:
    h, w = map(int, raw_input().split())
    if h == 0 and w== 0: break
    tmp = (w+1)/2
    s[0] = ('#.' * tmp)[:w]
    s[1] = ('.#' * tmp)[:w]
    for j in range(h):
        print s[j % 2]
    print
    