#include <bits/stdc++.h>
using namespace std;
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << H;
  debug_out(T...);
}
const int INF = 0x3f3f3f3f, m197 = (int)1e9 + 7;
void s_solve() {
  int a, b;
  cin >> a >> b;
  long long res = 0;
  for (int i = 0; i <= 30; ++i) {
    if (((a >> i) & 1) && !((b >> i) & 1))
      res += 1 << i;
    else if (!((a >> i) & 1) && ((b >> i) & 1))
      res += 1 << i;
  }
  cout << res << '\n';
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(10);
  int _T = 1, _C = 1;
  cin >> _T;
  while (_C++ <= _T) {
    s_solve();
  }
  return 0;
}
