#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    int a, b;
    scanf("%d %d", &a, &b);
    int temp = a & b;
    printf("%d\n", (a ^ temp) + (b ^ temp));
  }
}
