#include<bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> PII;
#define endl "\n"
#define ft first
#define sd second
#define pb push_back
const int MOD = 1e9 + 7;

void solve() {
	int la,lb,ra,rb;
	cin>>la>>ra>>lb>>rb;
	int cnt1 = ra - la + 1,cnt2 = rb - lb + 1;
	if(cnt1 <= 10 && cnt2 <= 10){
		int maxv = 0;
		for(int l1 = la;l1 <= ra;l1++){
			for(int l2 = lb;l2 <= rb;l2++){
				int sum = l1 + l2;
				while(sum){
					maxv = max(sum % 10,maxv);
					sum /=10;
				}
			}
		}
		cout<<maxv<<endl;
	}
	else cout<<9<<endl;
	return ;
}
signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int T = 1;
	cin>>T;
	while(T--)
		solve();
	return 0;
}