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

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, b, a) for(int i = (b) - 1; i >= (a); i--)
#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef double db;

int f(int x)
{
	string s = to_string(x);
	return *max_element(ALL(s)) - '0';
}

int main()
{
	ios::sync_with_stdio(0); 
	cin.tie(0);
	cout << fixed << setprecision(15);
	
	int t;
	cin >> t;
	while (t--)
	{
		int la, ra, lb, rb;
		cin >> la >> ra >> lb >> rb;
		int ans = 0;
		FOR (a, la, min(ra, la + 10) + 1)
		{
			FOR (b, lb, min(rb, lb + 10) + 1)
			{
				ans = max(ans, f(a + b));
			}
		}
		cout << ans << '\n';
	}
	
	return 0;
}