#include <bits/stdc++.h>
using namespace std;

using i64 = long long;

void solve() {
    int l1, r1, l2, r2;
    cin >> l1 >> r1 >> l2 >> r2;

    if (r1 - l1 >= 10 || r2 - l2 >= 10) {
        cout << 9 << endl;
    } else {
        auto work = [&](int x) -> int {
            int ret = x % 10;
            while (x > 0) {
                ret = max(ret, x % 10);
                x /= 10;
            }
            return ret;
        };

        int ans = 0;
        for (int i = l1; i <= r1; i++) {
            for (int j = l2; j <= r2; j++) {
                ans = max(ans, work(i + j));
            }
        }
        cout << ans << endl;
    }
}

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

    int t;
    cin >> t;

    while (t--) {
        solve();
    }

    return 0;
}