#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
using i64 = long long;

void solve()
{
    i64 la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    i64 L = la + lb, R = ra + rb;
    if (R - L >= 10)
        cout << 9 << endl;
    auto check = [&](i64 num) -> i64
    {
        i64 tmp = num, res = 0;
        while (tmp)
            res = max(res, tmp % 10), tmp /= 10;
        return res;
    };
    i64 ans = 0;
    for (i64 i = L; i <= R; i++)
    {
        ans = max(ans, check(i));
    }
    cout << ans << endl;
}

int main()
{
    ios::sync_with_stdio(false), cin.tie(0);
    int T = 1;
    cin >> T;
    while (T--)
        solve();
    // system("pause");
    return 0;
}