#include "bits/stdc++.h"

using namespace std;

#ifndef ONLINE_JUDGE
#include "test.h"
#include "dbg.h"
#else
#define debug(...) 42
#define debug_assert(...) 42
#endif


#define IOS ios::sync_with_stdio(0),cin.tie(0)

using ll = long long;
using ull = unsigned long long;

#define endl '\n'
#define int ll

using VI = vector<int>;
using VII = vector<VI>;
using PII = pair<int, int>;
const int inf = 1e18;
const int mod = 1e9 + 7;

void init() {
}


void solve() {
    int l1, r1, l2, r2;
    cin >> l1 >> r1 >> l2 >> r2;
    int l = l1 + l2;
    int r = r1 + r2;
    int maxs = -1;

    for (int i = 0; i <= 10; i++) {
        if (l + i > r)break;
        int t = l + i;
        while (t) {
            maxs = max(maxs, t % 10);
            t /= 10;
        }
    }
    cout << maxs << endl;
}

signed main() {
    IOS;
    init();
    // debug(1);
    int t = 1;
    cin >> t;
    while (t--) {
        solve();
    }
}