// duziteng ^ ^
#include <bits/stdc++.h>
using namespace std;
const int N = 5e5+10;
const int M = 998244353;
const int mod = 998244353;
#define db double
#define int long long
int up(int a,int b){return a<0?a/b:(a+b-1)/b;}
#define endl '\n'
#define all(x) (x).begin(),(x).end()
#define YES cout<<"Yes"<<endl;
#define NO cout<<"No"<<endl;
#define pi acos(-1)
#define INF 0x3f3f3f3f3f3f3f3f
#define PII pair<int,int>
#define fast ios::sync_with_stdio(false);cin.tie(nullptr);

void solve(){
    int la,ra,lb,rb;cin>>la>>ra>>lb>>rb;
    int ans=0;
    for(int a=la;a<=ra;a++){
        for(int b=lb;b<=rb;b++){
            int x=a+b;
            vector<int>nums;
            while(x)nums.push_back(x%10),x/=10;
            ans=max(ans,*max_element(all(nums)));
            if(ans==9){
                cout<<9<<endl;
                return;
            }
        }
    }
    cout<<ans<<endl;
}
signed main(){
    fast
    int t;t=1;cin>>t;
    while(t--) {
        solve();
    }
}