void conv(vec_ZZ_p& x, const vec_ZZ& a)
{
   long i, n;

   n = a.length();
   x.SetLength(n);

   ZZ_p* xp = x.elts();
   const ZZ* ap = a.elts();

   for (i = 0; i < n; i++)
      conv(xp[i], ap[i]);
}