#include <bits/stdc++.h>

using namespace std;

#ifdef DEBUG
  #include "debug.hpp"
#else
  #define dbg(...) 0
#endif

int calc_f(int x) {
  int ans = 0;
  while (x > 0) {
    ans = max(ans, x % 10);
    x /= 10;
  }
  return ans;
}

int solve(int la, int ra, int lb, int rb) {
  if (max(ra - la, rb - lb) >= 9) {
    return 9;
  }
  int ans = 0;
  for (int i = la; i <= ra; ++i) {
    for (int j = lb; j <= rb; ++j) {
      ans = max(ans, calc_f(i + j));
    }
  }
  return ans;
}

void test_case() {
  int la, ra, lb, rb;
  cin >> la >> ra >> lb >> rb;
  cout << solve(la, ra, lb, rb) << '\n';
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    test_case();
  }
}