#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
//#define int long long
//#define LL long long
#define endl "\n"
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define VI vector<int>
#define VVI vector<vector<int>>
#define PII pair<int,int>
#define MII map<int,int>
#define MSI map<string,int>
#define MAXN 0x3f3f3f3f
#define MINN -0x3f3f3f3f
#define Gheap priority_queue<int>
#define Lheap priority_queue<int,vector<int>,greater<int>>
using namespace std;
//const int N=1e6+100;
//int e[N],w[M],ne[M],h[M],idx;

int biggest(int n)
{
    stringstream ss;
    ss<<n;
    string s;
    ss>>s;
    int maxx=-1;
    for(int i=0;i<s.size();i++)
    {
        maxx=max(maxx,s[i]-'0');
    }
    return maxx;
}

void solve()
{
    int ans=-1;
    int la,ra,lb,rb;
    cin>>la>>ra>>lb>>rb;
    for(int i=la;i<=ra;i++)
    {
        for(int j=lb;j<=rb;j++)
        {
            ans=max(ans,biggest(i+j));
            if(ans==9) goto here;
        }
    }
    here:
    cout<<ans<<endl;
}

int main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t=1;
    cin >> t;
    while(t--) solve();
}