#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <map>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <climits>
#include <cassert>
using namespace std;

ifstream fin("C.txt");
#define cin fin

unsigned long
solve(vector<unsigned long>& data, unsigned long sumk)
{
  unsigned long k = 0;
  for(unsigned long mask = 1UL; mask; mask <<= 1) {
    unsigned long ksum = 0UL;
    for(int j = 0; j < data.size(); j++)
      ksum += data[j];
    
    if((ksum ^ sumk) & mask) {
      k |= mask;
      sumk ^= mask;
      for(int j = 0; j < data.size(); j++)
	data[j] ^= mask;
    }
  }
  return k;
}

int main()
{
  if(!fin) return -1;
  
  int S; cin >> S;
  while(S--) {
    vector<unsigned long> data;
    string s;
    for(int i = 0; i < 9; i++) {
      cin >> s;
      data.push_back((unsigned long) strtoll(s.c_str(), NULL, 16));
    }
    unsigned long sum = data.back(); data.pop_back();
    static char buffer[32];
    sprintf(buffer, "%lx", solve(data, sum));
    cout << buffer << endl;
  }
  return 0;
}