while 1:
    h,w=map(int,raw_input().split())
    if h==w==0: break
    ans=[['.' for v in range(w)] for x in range(h)]
    for i in range(h):
        for j in range(i%2,w,2):
            ans[i][j]='#'
    for i in range(h):
        print ''.join(ans[i])
    print ''