public static int gcd(int x, int y)
    {
        int t;

        if(x < 0) x = -x;
        if(y < 0) y = -y;

        while(y != 0)
        {
            if(y > x)
            {
                x = y-x;
                y = y-x;
                x = x+y;
            }

            if(y == 0) return x;

            t = y;
            y = x%y;
            x = t;
        }
        return Math.abs(x);
    }