#include<bits/stdc++.h>
#define int long long 
#define PII pair<int,int>
#define x first
#define y second
using namespace std;
int check(int x){
	int n=0;
	while(x){
		n=max(x%10,n);
		x/=10;
	}
	return n;
}
void solve(){
	int a,b,c,d;
	cin>>a>>b>>c>>d;
	a+=c;
	b+=d;
	int now=0;
	for(int i=a;i<=b;i++){
		now=max(check(i),now);
		if(now==9) break;
	}
	cout<<now<<"\n";
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	int T=1;
	cin>>T;
	while(T--){
		solve();
	}
	return 0;
}