//  __      __          ___                                         ___    __ __
// /\ \  __/\ \        /\_ \                                      /'___'\ /\ \ \
// \ \ \/\ \ \ \     __\//\ \     ___    ___     ___ ___      __ /\_\ /\ \ \ \ \       __   __  __     __   _ __
//  \ \ \ \ \ \ \  /'__'\ \ \   /'___\ / __'\ /' __' __'\  /'__'\/_/// /__\ \ \ \_   /'__'\/\ \/\ \  /'__'\/\''__\
//   \ \ \_/ \_\ \/\  __/ \_\ \_/\ \__//\ \L\ \/\ \/\ \/\ \/\  __/  // /_\ \ \__ ,__\/\  __/\ \ \_/ |/\  __/\ \ \/
//    \ '\___x___/\ \____\/\____\ \____\ \____/\ \_\ \_\ \_\ \____\/\______/ \/_/\_\_/\ \____\ \___/ \ \____\ \_\
//     '\/__//__/  \/____/\/____/\/____/\/___/  \/_/\/_/\/_/\/____/\/_____/     \/_/   \/____/ \/__/   \/____/ \/_/
//   bilibili:24Records
//   link:https://space.bilibili.com/3546387113314828
//   blog link:https://welcome24ever.github.io/24Records/
//
//   Then,we just singing like.
//   Welcome To Forever.
#include "bits/stdc++.h"
using namespace std;
const int Welcome24ever = 0;
#define endl '\n'
#define fixset(x) fixed << setprecision(x)
//#define int long long
typedef long long ll; typedef pair<int,int> PII;
long double pi = acos(-1);
const int MOD = 998244353; const int N = 5e5+5;
void NeverSayNever() {
    int la,ra,lb,rb; cin >> la >> ra >> lb >> rb;
    auto check = [&](int x,int y)->int{
        int tmp = x + y;
        string str = to_string(tmp);
        auto mx = *max_element(str.begin(), str.end());
        return mx - '0';
    };
    if(ra - la >= 9 || rb - lb >= 9){
        cout << 9 << endl;
    }else{
        int ans = 0;
        for (int i = la; i <= ra ; ++i) {
            for (int j = lb; j <= rb ; ++j) {
                ans = max(ans,check(i,j));
            }
        }
        cout << ans << endl;
    }
}
signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int T = 1;
    cin >> T;
    while (T--) {
        NeverSayNever();
    }
    return Welcome24ever;
}