def sup_of_layouts(layout1, layout2):
        """ Return the least layout compatible with layout1 and layout2 """
        if len(layout1) > len(layout2):
                layout1, layout2 = layout2, layout1
        if len(layout1) < len(layout2):
                layout1 += [0] * (len(layout2) - len(layout1))
        return [max(layout1[i], layout2[i]) for i in xrange(len(layout1))]
Return the least layout compatible with layout1 and layout2