#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define int long long
#define double long double
#define x first
#define y second
#define pb push_back
using namespace std;
using pii=pair <int,int>;
using tii=pair <pii,int>;
using rii=pair <int,pii>;
using qii=pair <pii,pii>;
using namespace __gnu_pbds;
const int mod=998244353LL;
void solve(){
    int la,ra,lb,rb;
    cin>>la>>ra>>lb>>rb;
    if (ra-la>=10||rb-lb>=10){
        cout<<"9\n";
        return;
    }
    int ans=0;
    for (int i=la; i<=ra; i++){
        for (int j=lb; j<=rb; j++){
            int tp=i+j,r=0;
            while (tp){
                r=max(r,tp%10);
                tp/=10;
            }
            ans=max(ans,r);
        }
    }
    cout<<ans<<'\n';
}
signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int t=1;
    cin>>t;
    while (t--) solve();
}