// Initialize b = a^((m+1)/2), c = a^m, but avoid to divide by a.
var cl_MI c = R->expt_pos(a,(m-1)>>1);
var cl_MI b = R->mul(a,c);
// Initialize b = a^((m+1)/2), c = a^m, but avoid to divide by a.
var cl_MI c = R->expt_pos(a,(m-1)>>1);
var cl_MI b = R->mul(a,c);