def get_merged_header(*lines):
    h = [[_f for _f in _h.split(" ") if _f] for _h in lines]
    header = []
    if len(h) == 0 or any(len(h[i]) != len(h[i + 1]) for i in range(len(h) - 1)):
        return header
    for idx in range(len(h[0])):
        header_i = h[0][idx]
        for jdx in range(len(h) - 1):
            if h[jdx + 1][idx] == ".":
                break
            header_i += " " + h[jdx + 1][idx]
        header.append(header_i)
    return header