#include <map>
#include <set>
#include <array>
#include <cmath>
#include <deque>
#include <bitset>
#include <random>
#include <string>
#include <vector>
#include <cassert>
#include <complex>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>

using namespace std;

void solve() {
    
    long long la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    long long mn = la + lb;
    long long mx = ra + rb;
    if (mx - mn >= 10) {
        cout << 9 << '\n';
    } else {
        long long ans = 0;
        for (long long x = mn; x <= mx; ++x) {
            long long tmp = x;
            while (tmp) {
                ans = max(ans, tmp % 10);
                tmp /= 10;
            }
        }
        cout << ans << '\n';
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}