#include<bits/stdc++.h>
using namespace std;
#define fast ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define int long long
int n,m;
int la,lb,ra,rb;
const int N=2e6+7;
const int mod=998244353;

void solve(){
    cin>>la>>ra>>lb>>rb;
    int a=la+lb,b=ra+rb;
    if(b>=a+10)
    {
        cout<<9<<endl;return;
    }
    int maxn=0;
    for(int i=a;i<=b;i++)
    {
        int tp=i;
        while(tp)
        {
            maxn=max(maxn,tp%10);
            tp/=10;
        }
    }
    cout<<maxn<<endl;
}
signed main(){
    fast;
    int t=1;
    cin>>t;
    while(t--){
        solve();
    }
}