#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
typedef long long ll;

void solve()
{
    int la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    int l = la + lb, r = ra + rb;
    if (r / 10 > l / 10)
        cout << "9\n";
    else
    {
        int ans = 0;
        while (r)
            ans = max(ans, r % 10), r /= 10;
        cout << ans << '\n';
    }
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int T;
    cin >> T;
    while (T--)
        solve();
    // solve();
    return 0;
}