// Paar (x, y) einer elliptischen Kurve

import java.math.BigInteger;

  // Hilfsklasse: Paar x und y in
  public final class Paar_ECM
  {
    public BigInteger x;
    public BigInteger y;

    public final static BigInteger BM1 = BigInteger.valueOf(-1);
    public final static Paar_ECM NEUTRAL = new Paar_ECM(BM1, BM1);

    public Paar_ECM (int para_x, int para_y)
    {
      x = BigInteger.valueOf(para_x); y = BigInteger.valueOf(para_y);
    }

    public Paar_ECM (BigInteger para_x, BigInteger para_y)
    {
      x = para_x; y = para_y;
    }

    public final boolean istNeutral()
    {
      return (x.equals(BM1) && y.equals(BM1) );
    }

    public final String toString()
    {
      return ("x=" + x.toString() + ", y=" + y.toString());
    }

    public final boolean istNegativ(Paar_ECM gegner, BigInteger n)
    {
      return (x.equals(gegner.x) && y.equals(n.subtract(gegner.y)));
    }
  }