def make_vmap(ru,rd):
    """return a dict mapping ids in the notation to their rust variable names"""
    r = {x:'v'+x[0] for x in "z0 z1 z2 z3 a0 a1 a2 a3".split()}
    r.update({x:'vu' for x in ru})
    r.update({x:'vd' for x in rd})
    return r