#pragma GCC optimize(3, "Ofast", "inline")
#include <iostream>
#include <bits/stdc++.h>
#define IOS ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
#define INF 0x3f3f3f3f
#define L_INF 0x7f3f3f3f3f3f3f3f
#define db cout << "debug\n";

using namespace std;
const int Mod = 998244353;
using ll = long long;
ll la, lb, ra, rb, L, R, maxn;

void solve()
{
    cin >> la >> ra >> lb >> rb;
    L = la + lb;
    R = ra + rb;
    if (R - L >= 9 || R % 10 < L % 10)
    {
        cout << "9\n";
        return;
    }
    maxn = 0;
    while (R != 0)
    {
        maxn = max(maxn, R % 10);
        R /= 10;
    }
    cout << maxn << '\n';
}
int main()
{
    IOS;
// freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
#ifndef ONLINE_JUDGE
    clock_t start_time = clock();
#endif
    int t = 1;
    cin >> t;
    while (t--)
    {
        solve();
    }
#ifndef ONLINE_JUDGE
    cout << "Used " << (double)(clock() - start_time) << " ms" << endl;
#endif
    return 0;
}