#include<bits/stdc++.h>
#define ll long long
#define ssz(x) ((int)x.size())
using namespace std;
const int N=3e5+5;
int n,m;
inline int red(){
	int data=0;bool w=0;char ch=getchar();
	while(ch!='-' && (ch<'0' || ch>'9'))ch=getchar();
	if(ch=='-') w=1,ch=getchar();
	while(ch>='0' && ch<='9') data=(data<<3)+(data<<1)+ch-'0',ch=getchar();
	return w?-data:data;
}
int get(int x){
	int ret=0;
	while(x){
		ret=max(ret,x%10);
		x/=10;
	}
	return ret;
}
void solve(){
	int l1=red(),r1=red(),l2=red(),r2=red();
	if(r1-l1+1>10||r2-l2+1>10){
		puts("9");
		return;
	}
	int ans=0;
	for(int i=l1;i<=r1;i++)
		for(int j=l2;j<=r2;j++)
			ans=max(ans,get(i+j));
	cout<<ans<<"\n";
}
int main()
{
	//ios::sync_with_stdio(false);
	//cin.tie(0);
	//cout.tie(0); 
	int T=red();
	while(T--)solve();
	return 0;
}