Where i am wrong

code

public void solve(int testNumber, FastReader scan, PrintWriter out) {

        int a  = scan.nextInt();
        int b = scan.nextInt();

        int sum  = Integer.MIN_VALUE;

        int q1 = a^a;
        int q2 = b^b;
        int q3 = a^b;

        if(q1 >= sum){
            sum = q1;
        }
        if(q2 >= sum){
            sum = q2;
        }

        if(q3 >=sum){
            sum = q3;
        }

       // int[] arr = new int[n];


        out.println(sum);

    }

for 8 & 20 your output should be 31 .
debug for this