while True:
    H, W = map(int, input().split())
    if H == 0 and W == 0:
        break
    
    c = ""
    for i in range(H):
        if i % 2 == 0:
            for j in range(W):
                if j % 2 == 0:
                    c += "#"
                else:
                    c += "."
            c += "\n"
        else:
            for k in range(W):
                if k % 2 == 0:
                    c += "."
                else:
                    c += "#"
            c += "\n"
    print(c)
    print()
