#include<bits/stdc++.h>
using namespace std;
#define int long long
#define io_speed_up ios::sync_with_stdio(0),cin.tie(0)

int T;
int la,lb,ra,rb;

int f(int a){
	int c=a;
	int ans=0;
	while(c){
		ans=max(ans,c%10);
		c/=10;
	}
	return ans;
}

void solve(){
	cin>>la>>ra>>lb>>rb;
	if(ra-la>=15||rb-lb>=15){
		cout<<9<<endl;
	}
	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<<endl;
	}
}

signed main(){
	io_speed_up;
	cin>>T;
	while(T--){
		solve();
	}
	return 0;

}