#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using i64=long long;
using u64=unsigned long long;
void solve(){
    ll la,ra,lb,rb;
    cin>>la>>ra>>lb>>rb;
    if(ra-la>=9||rb-lb>=9){
        cout<<"9"<<"\n";
        return;
    }
    auto check=[&](ll x)->int{
        string s=to_string(x);
        int mx=0;
        for(auto x:s){
            mx=max(mx,x-'0');
        }
        return mx;
    };
    int ans=0;
    for(int i=la;i<=ra;i++){
        for(int j=lb;j<=rb;j++){
            ans=max(ans,check(i+j));
        }
    }
    cout<<ans<<"\n";
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t;
    cin>>t;
    while(t--) solve();
    return 0;
}