#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pii;
bool chmin(int &x, int y) {
	if (x > y) {
		x = y;
		return 1;
	}
	return 0;
}
bool chmax(int &x, int y) {
	if (x < y) {
		x = y;
		return 1;
	}
	return 0;
}
void solve() {
	int la, ra, lb, rb;
	cin >> la >> ra >> lb >> rb;
	vector<int> a, b;
	for (int i = la; i <= min(la + 9, ra); i ++) {
		a.push_back(i);
	}

	for (int i = lb; i <= min(lb + 9, rb); i ++) {
		b.push_back(i);
	}

	auto cal = [&](int x) -> int{
		int res = 0;
		while (x) {
			chmax(res, x % 10);
			x /= 10;
		}
		return res;
	};	

	int ans = 0;
	for (int x : a) {
		for (int y : b) {
			chmax(ans, cal(x + y));
		}
	}
	cout << ans << '\n';
}

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

	return 0;
}