#include<cstdio>
#include<cstring>
#include<iostream>
#include<cmath>
using namespace std;
long long la,ra,lb,rb;
char a[11],b[11],c[11],d[11];
void solve()
{
	cin>>la>>ra>>lb>>rb;
	if(ra-la>=9||rb-lb>=9){
		cout<<"9"<<endl;
		return;
	}
	long long maxn=0;
	for(long long i=la;i<=ra;i++)
	{
		for(long long j=lb;j<=rb;j++)
		{
			long long now=i+j;
			while(now)
			{
				maxn=max(maxn,now%10);
				now/=10;
			}
		}
	}
	cout<<maxn<<endl;
	return;
}
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
		solve();
	}
	return 0;
}