#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <vector>
#include <set>
#include <queue>
#include <map>
#define endl '\n'
#define int long long
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define rep2(i,a,b) for(int i=(a);i>=(b);i--)
using namespace std;
template<typename... Args>
void bubu(Args... args) { cout << ":: "; ((cout << args << " "), ...); cout << endl; }
void bubu(vector<int> tem) { for (auto x : tem) cout << x << ' '; cout << endl; }
void kuaidu() { ios::sync_with_stdio(false), cin.tie(0), cout.tie(0); }
inline int max(int a, int b) { if (a < b) return b; return a; }
inline int min(int a, int b) { if (a < b) return a; return b; }
using PII = pair<int, int>;
using i128 = __int128;

//=======================================================================
const int N = 1e5 + 10;
const int M = 1e6 + 10;
const int mod = 1e9 + 7;
const int INF = 1e16;
int n, m, T;

//=======================================================================

signed main() {
    kuaidu();
    cin >> T;
    while (T--) {
        int l1, l2, r1, r2;
        cin >> l1 >> r1 >> l2 >> r2;

        int c1, c2;
        c1 = r1 - l1, c2 = r2 - l2;
        if (c1 >= 10 || c2 >= 10) {
            cout << 9 << endl;
            continue;
        }
        int ans = 0;
        rep(i, l1, r1) {
            rep(j, l2, r2) {
                int x = i + j;
                while (x) {
                    ans = max(ans, x % 10); x /= 10;
                }
            }

        }
        cout << ans << endl;
    }
    return 0;
}