#include <bits/stdc++.h>

#define x first
#define y second
#define el '\n'
#define debug(x) cerr << #x << ": " << x << endl
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int N = 3e5 + 10, INF = 0x3f3f3f3f, mod = 998244353;

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

void solve() {
    int la, ra, lb, rb; cin >> la >> ra >> lb >> rb;
    int l = la + lb, r = ra + rb;
    int ans = get(l);
    for (int i = 0; i < 10; ++i) {
        ++l;
        if (l > r) break;
        ans = max(ans, get(l));
    }
    cout << ans << el;
}

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