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