#include<bits/stdc++.h>
using namespace std;
#define int long long
#define PI pair<int,int>
bool cmp(PI a,PI b){
    if(a.first==b.first)return a.second>b.second;
    else return a.first<b.first;
}
const int inf=1e9;
string ch="edocteel";  
int dp[2020];
struct node{
    int x,y,gcd;
};
int gcdd(int x,int y){
    if(!y)return x;
    else return gcdd(y,x%y);
}
signed main(){
 ios::sync_with_stdio(false);
 cin.tie(0);cout.tie(0);
    int t;
    cin>>t;
    while(t--){
        int la,ra,lb,rb;
        cin>>la>>ra>>lb>>rb;
        la+=lb;
        ra+=rb;
        if(ra-la>10)cout<<9<<"\n";
        else{
            int maxx=0;
            for(int i=la;i<=ra;i++){
                int tmp=i;
                while(tmp){
                    maxx=max(tmp%10,maxx);
                    tmp/=10;
                }
            }
            cout<<maxx<<'\n';
        }
    }
    return 0;
}