#include<bits/stdc++.h>
#define int  long long
using namespace std;
int ans;
int divide(int n)
{
    int x=-1;
    while(n)
    {
        int t=n%10;
        x=max(t,x);
        n/=10;
    }
    return x;
}

signed main()
{
    int T;
    cin>>T;
    while(T--)
    {
        ans=0;
        int la,ra,lb,rb;
        cin>>la>>ra>>lb>>rb;
        int l=la+lb,r=ra+rb;
        if(r-l>=9)
        {
            cout<<"9\n";
            continue;
        }
        for(int i=l;i<=r;i++)
        {
            ans=max(divide(i),ans);
        }
        cout<<ans<<endl;
     }
    return 0;
}