int a = 2;
        int b = 3;
       System.out.println(a +": "+ b  );
        a = b - a;
        b = b - a; 
        a = a + b;
        System.out.println(a +": "+ b  );
        a = a^b;
        b = a^b;
        a = a^b;
        System.out.println(a +": "+ b  );