public Xint toPowerOf(int n) {
   cnt.sqr++;
   return new Xint(ApintMath.pow(api, n));
 }
 public Xint shiftLeft(int b) {
   cnt.lsh++;
   return new Xint(ApintMath.scale(api, b));
 }
 public Xint gcd(Xint b) {
   return new Xint(ApintMath.gcd(api, b.api));
 }