#include <bits/stdc++.h>

using i64 = long long;

void sol() {
    int la, ra, lb, rb;
    std::cin >> la >> ra >> lb >> rb;

    if (ra - la + 1 >= 10 || rb - lb + 1 >= 10) {
        std::cout << 9 << "\n";
        return;
    }

    auto cal = [](i64 t) {
        int x = 0;
        while (t) {
            int temp = t % 10;
            t /= 10;
            x = std::max(temp, x);
        }
       return x;
    };

    int ans = 0;

    for (int i = la; i <= ra; i++) {
        for (int j = lb; j <= rb; j++) {
            i64 t = i + j;
            ans = std::max(ans, cal(t));
        }
    }

    std::cout << ans << "\n";
}

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

    int _;
    std::cin >>_;

    while (_--) {
        sol();
    }

    return 0;
}