#include<bits/stdc++.h>
using namespace std;
int f(int x)
{
  int maxn = 0;
  while(x)
  {
    maxn = max(maxn, x % 10);
    x /= 10;
  }
  return maxn;
}
void solve(){
  int la, ra, lb, rb;
  cin >> la >> ra >> lb >> rb;
  int l = la + lb, r = ra + rb;
  if(r - l >= 9)
  {
    cout << "9\n";
    return;
  }
  else
  {
    int ans = 0;
    for(int i = l; i <= r; i ++ )
    {
      ans = max(ans, f(i));
    }
    cout << ans << endl;
  }
}
int main(){
  int T;
  cin >> T;
  while(T -- )
  {
    solve();
  }

  return 0;
}