#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

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

    int t;
    cin >> t;

    while (t--) {
        int la, ra, lb, rb;
        cin >> la >> ra >> lb >> rb;
        if ((i64)(ra - la) * (rb - lb) >= 100) {
            cout << 9 << '\n';
        } else {
            i64 ans = 0;
            for (i64 i = la; i <= ra; i++)
                for (i64 j = lb; j <= rb; j++) {
                    i64 k = i + j;
                    for ( ; k; k /= 10)
                        ans = max(ans, k % 10);
                }
            cout << ans << '\n';
        }
    }
}