public static long[] GCD(long a, long b)
        {
            /*
               Test Data used:

             */

            long[] U = new long[3] { a, 0, 1 };
            long[] V = new long[3] { b, 1, 0 };
            long[] dxy = new long[3];
            long r, q;

            while (b > 0)
            {
                q = a / b;
                r = a - q * b;
                dxy[1] = U[2] - q * U[1];
                dxy[2] = V[2] - q * V[1];
                a = b;
                b = r;
                U[2] = U[1];
                U[1] = dxy[1];
                V[2] = V[1];
                V[1] = dxy[2];
            }

            dxy[0] = a;
            dxy[1] = U[2];
            dxy[2] = V[2];
            return dxy;
        }