#include<bits/extc++.h>
using namespace __gnu_pbds;
using namespace std;
using ll=long long;
#define LNF 0x3f3f3f3f3f3f3f3f
#define INF 0x3f3f3f3f
template <class T> using Tree = tree<T, null_type, less<T>,rb_tree_tag, tree_order_statistics_node_update>;
#define pll pair<int,int>
void solve(void){
    ll la,ra,lb,rb;
    cin>>la>>ra>>lb>>rb;
    auto get=[](ll x){
        ll ma=0;
        while(x){
            ma=max(ma,x%10);
            x/=10;
        }
        return ma;
    };   
    ll ans=0;
    for(ll i=la;i<=ra;i++){
        for(ll j=lb;j<=rb;j++){
            ans=max(ans,get(i+j));
            if(ans==9){
                cout<<ans<<"\n";
                return;
            }
        }
    }
    cout<<ans<<"\n";
}
int main() {
    ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
    int t=1;
    cin>>t;
    while(t--)
    solve();
    return 0;
}