#include <bits/stdc++.h>
#define N (200000 + 10)  /*------------------ #define ------------------*/
#define M (400000 + 10)
#define MOD (1000000000 + 7)
//#define MOD (998244353)
#define INF (0x3f3f3f3f)
#define LNF (3e18)
#define mod(a,b) (((a)%(b)+(b))%(b))
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
#define fi first
#define se second
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int> PII;
typedef pair<LL,LL> PLL;
typedef pair<int,LL> PIL;
typedef pair<LL,int> PLI;
typedef pair<double,double> PDD;

int la,ra,lb,rb;

auto solve(){
	
	cin >> la >> ra >> lb >> rb;
	
	auto f = [&](int x){
		int ans = 0;
		while(x){
			ans = max(ans,x % 10);
			x /= 10;
		}
		return ans;
	};
	
	int L1 = (ra - la + 1),L2 = (rb - lb + 1);
	if(L1 >= 10 || L2 >= 10){
		cout << "9\n";
	}else{
		int ans = 0;
		for(int i = la;i <= ra;i ++ )
			for(int j = lb;j <= rb;j ++ )
				ans = max(ans,f(i + j));
		cout << ans << '\n';
	}
	
}

signed main(){
	IOS
	int T = 1;
	//
	cin >> T;
	while(T -- ) solve();
	//while(T -- ) cout << (solve() ? "YES" : "NO") << '\n';

    return 0;
}