#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;
        set<int> cnt[15];
        set<int> cnt2[15];
        rep(i, 0, 13) cnt[i].clear(), cnt2[i].clear();
        int l = 0;
        while (r1) {
            int cha = r1 / 10 - l1 / 10;
            if (cha >= 2) {
                rep(i, 0, 9)
                    cnt[l].insert(i);
                l++;
                l1 /= 10, r1 /= 10;
                continue;
            }
            int x = l1, y = r1;
            rep(i, x, y) cnt[l].insert(i % 10);
            l++;
            l1 /= 10, r1 /= 10;
        }
        int len = l;
        l = 0;
        while (r2) {
            int cha = r2 / 10 - l2 / 10;
            if (cha >= 2) {
                rep(i, 0, 9)
                    cnt2[l].insert(i);
                l++;
                l2 /= 10, r2 /= 10;
                continue;
            }
            int x = l2, y = r2;
            rep(i, x, y) cnt2[l].insert(i % 10);
            l++;
            l2 /= 10, r2 /= 10;
        }
        int ans = 0;

        l = max(l, len);
        rep(i, 0, l - 1) {
            if (cnt[i].empty()) cnt[i].insert(0);
            if (cnt2[i].empty()) cnt2[i].insert(0);
            for (auto x : cnt[i]) for (auto y : cnt2[i]) {
                ans = max(ans, ((x + y) % 10));
            }
        }
        cout << ans << endl;

    }
    return 0;
}