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

#define ll long long
#define MOD 998244353
#define pii pair<int, int>

int cnt(int x) {
    return x ? max(x % 10, cnt(x / 10)) : 0;
}

int main() {
#ifdef TEST
    freopen("zz.in", "r+", stdin);
#endif
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int t; cin >> t;
    while (t --) {
        int a, b, c, d; cin >> a >> b >> c >> d;
        a += c, b += d;
        
        if (b - a + 1 >= 10) {
            cout << 9 << '\n';
        } else {
            int res = 0;
            for (int i = a; i <= b; ++ i) res = max(res, cnt(i));
            cout << res << '\n';
        }
    }

    return 0;
}