#include <bits/stdc++.h>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pdd pair<double, double>
#define vi vector<int>
#define vll vector<long long>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<long long, long long>>
#define vpdd vector<pair<double, double>>
#define mp make_pair
#define fi first
#define se second
#define all(v) v.begin(), v.end()
#define pb push_back
#define endl "\n"
#define vvi vector<vector<int>>
#define vvll vector<vector<long long>>

using namespace std;
using LL = long long;
using ULL = unsigned long long;
const int N = 2e5 + 10, INF = 0x3f3f3f3f, mod = 998244353;
const LL bigINF = ((ULL)(1) << 63) - 1;
const double eps = 1e-6;

void Sol()
{
    int l1, r1, l2, r2;
    cin >> l1 >> r1 >> l2 >> r2;
    if(r1 - l1 >= 10 || r2 - l2 >= 10) {
        cout << 9 << endl;
    } else {
        LL ans = -1;
        for (int i = l1; i <= r1; i++)
        {
            for (int j = l2; j <= r2; j ++ ) {
                LL num = i + j;
                while(num) {
                    ans = max(ans, num % 10);
                    num /= 10;
                }
            }
        }
        cout << ans << endl;
    }
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);

    int t = 1;
    cin >> t;
    while (t--)
    {
        Sol();
    }

    return 0;
}