#include<bits/stdc++.h>
using namespace std;
int f(int x)
{
    int res=0;
    while(x)
    {
        res=max(res,x%10);
        x/=10;
    }
    return res;
}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        int la,ra,lb,rb;
        cin>>la>>ra>>lb>>rb;
        int res=0;
        vector<int>p,q;
        for(int i=la;i<=la+10&&i<=ra;i++)
            p.push_back(i);
        for(int i=ra;i>=ra-10&&i>=la;i--)
            p.push_back(i);
        for(int i=lb;i<=lb+10&&i<=rb;i++)
            q.push_back(i);
        for(int i=rb;i>=rb-10&&i>=lb;i--)
            q.push_back(i);
        for(auto &x:p)
            for(auto &y:q)
                res=max(res,f(x+y));
        cout<<res<<endl;
    }
    return 0;
}