code: func (x Pol) MulMod(f, g Pol) Pol {
  	if x == 0 || f == 0 {
  		return 0
  	}
  
  	var res Pol
  	for i := 0; i <= f.Deg(); i++ {
  		if (f & (1 << uint(i))) > 0 {
  			a := x
  			for j := 0; j < i; j++ {
  				a = a.Mul(2).Mod(g)
  			}
  			res = res.Add(a).Mod(g)
  		}
  	}
  
  	return res
  }
docs: // MulMod computes x*f mod g