#include <bits/stdc++.h>
using namespace std;
#define int long long
void solve()
{
    int l1, r1, l2, r2;
    cin >> l1 >> r1 >> l2 >> r2;
    if(r1 - l1 + 1 >= 10 || r2 - l2 + 1 >= 10)
    {
        cout << 9 << endl;
    }
    else 
    {
        int ans = 0;
        for (int i = l1; i <= r1; i++)
        {
            for (int j = l2; j <= r2; j++)
            {
                int s = i + j;
                string ss = to_string(s);
                for (int p = 0; p < ss.size(); p++)
                    ans = max(ans, (int)(ss[p]- '0'));
            }
        }
        cout << ans << endl;
    }
}
signed main()
{
    int t;
    cin >> t;
    while(t--) solve();
}