#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define range(x) (x).begin(), (x).end()
const int dir[][2] = {1, 0, -1, 0, 0, 1, 0, -1};

void solve()
{
    int l1, r1, l2, r2;
    cin >> l1 >> r1 >> l2 >> r2;
    if (r1 - l1 >= 10 || r2 - l2 >= 10) {
        cout << "9\n";
        return;
    }
    int ans = 0;
    for (int i = l1; i <= r1; ++i) {
        for (int j = l2; j <= r2; ++j) {
            string s = to_string(i + j);
            for (auto e : s)
                ans = max(ans, e - '0');
        }
    }
    cout << ans << '\n';
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int t = 1;
    cin >> t;
    while (t--)
        solve();
    return 0;
}