#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef unsigned long long ull;

int f(int x)
{
    int ans = 0;
    while (x) ans = max(ans, x % 10), x /= 10;
    return ans;
}

void sol()
{
    int la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    if ((ra - la) + (rb - lb) >= 9) {cout << "9\n";}
    else
    {
        int ans = 0;
        for (int i = la; i <= ra; i ++)
        {
            for (int j = lb; j <= rb; j ++)
            {
                ans = max(ans, f(i + j));
            }
        }
        cout << ans << '\n';
    }
}

int main()
{
    ios::sync_with_stdio(0); cin.tie(0);
    int T = 1;
    cin >> T;
    while (T --) sol();
    return 0;
}