#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define int long long
const int N=1e5+5;
ll f(int x)
{
    ll ans=0;
    while(x)
    {
        ans=max(x%10,ans);
        x/=10;
    }
    return ans;
}
void solve()
{
    int a,b,c,d;cin>>a>>b>>c>>d;
    if(b-a+d-c>12)
    {
        cout<<9<<endl;
    }
    else 
    {
        ll ans=0;
        for(int i=a;i<=b;i++)
        {
            for(int j=c;j<=d;j++)
            {
                ll cnt=i+j;
                ans=max(ans,f(cnt));
            }
        }
        cout<<ans<<endl;
    }
}
signed main()
{
    std::ios::sync_with_stdio(false); 
    std::cin.tie(nullptr);std::cout.tie(nullptr);
    // FILE* stream1;
    // freopen_s(&stream1, "data.txt", "r", stdin);
    // freopen_s(&stream1, "out.txt", "w", stdout);
    int t;t=1;
    std::cin>>t;
    while(t--)solve();
}