#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}
inline double time() {
    return static_cast<long double>(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count()) * 1e-9;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int q; cin >> q;
    while (q--) {
        int a,b,c,d; cin >> a >> b >> c >> d;
        int res = 0;
        auto cal = [&](int x) -> int {
            int mx = 0;
            while (x) {
                mx = max(mx, x%10);
                x /= 10;
            }
            return mx;
        };
        for (int i = a; i <= b; ++i) {
            for (int j = c; j <= d; ++j) {
                res = max(res, cal(i+j));
                if (res == 9) break;
            }
            if (res == 9) break;
        }
        cout << res << "\n";
    }
}