#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
typedef pair<double, double> PDD;
typedef unsigned long long ull;

void solve() {
    int la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    if (ra - la + 1 >= 10 || rb - lb + 1 >= 10) {
        cout << 9 << '\n';
    } else {
        int ans = 0;
        for (int i = la; i <= ra; i++) {
            for (int j = lb; j <= rb; j++) {
                int x = i + j, res = 0;
                while (x) {
                    ans = max(ans, x % 10);
                    x /= 10;
                }
            }
        }
        cout << ans << '\n';
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
    cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}