#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb push_back
#define fi first
#define se second

void solve() {
	ll la, ra, lb, rb;
	cin >> la >> ra >> lb >> rb;

	ll x = la + lb;
	ll k = min(ra + rb, x + 10);

	ll mx = 0;
	for (ll i = x ; i <= k ; i++) {
		ll t = i;
		while (t) {
			mx = max(mx, t % 10);
			t /= 10;
		}
	}
	cout << mx << '\n';
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t = 1;
	cin >> t;
	while (t--)
		solve();
	return 0;
}