#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int t;
ll la,ra,lb,rb;
ll num(ll x){
	ll res=0;
	while(x){
		x/=10;
		res++;
	}
	return res;
}
ll getans(ll x){
	ll ans=0;
	while(x){
		ans=max(ans,x%10);
		x/=10;
	}
	return ans;
}
ll ksm(int p){
	ll res=1,base=10;
	while(p){
		if(p%2) res*=base;
		base*=base;
		p/=2;
	}
	return res;
}
int main(){
	scanf("%d",&t);
	while(t--){
		scanf("%lld%lld%lld%lld",&la,&ra,&lb,&rb);
		ll mn,mx;
		mn=la+lb;mx=ra+rb;
		//cin>>mn>>mx;
		ll a=mn,b=mx;
		if(b-a>=9){
			cout<<9<<endl;
			continue;
		}
		if(num(a)==num(b)){
			int f=1;
			while((a>10)&&(b>10)){
				ll ans1,ans2;
				ans1=a/(ksm(num(a)-1));
				ans2=b/(ksm(num(b)-1));
				if(ans1!=ans2){
					cout<<9<<endl;
					f=0;
					break;                                             
				}
				a%=(ksm(num(a)-1));
				b%=(ksm(num(b)-1));
			}
			if(f){
				cout<<max(getans(mn),getans(mx))<<endl;
			}
		}
		else cout<<9<<endl;
	}
	return 0;
}