#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define Mp make_pair
#define pb push_back

typedef double db;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

void solve() {
    ll la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    if(ra - la + 1 >= 10 || rb - lb + 1 >= 10) {
        cout << "9\n";
    } else {
        ll ans = 0;
        auto f = [&](ll x) {
            ll res = 0;
            while(x) res = max(res, x % 10), x /= 10;
            return res;
        };
        for(ll a = la; a <= ra; a++)
            for(ll b = lb; b <= rb; b++) {
                ans = max(ans, f(a + b));
            }
        cout << ans << '\n';
    }
}
signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int t = 1;
    cin >> t;
    while(t--) solve();
    return 0;
}