#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e5 + 5;
int __t = 1, n;
void solve() {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    int ans = 0;
    for (int i = a; i <= b && i <= a + 10; i++) {
        for (int j = c; j <= d && j <= c + 10; j++) {
            int x = i + j;
            while (x) {
                int y = x % 10;
                ans = max(ans, y);
                x /= 10;
            }
        }
    }
    cout << ans << '\n';
    return;
}
int32_t main() {
#ifdef ONLINE_JUDGE
    ios::sync_with_stdio(false);
    cin.tie(0);
#endif
    cin >> __t;
    while (__t--)
        solve();
    return 0;
}