#include <bits/stdc++.h>
#define tests
#define int long long
const int N = 1e5 + 10;
using namespace std;
using LL = long long;

int f(int a) {
    int mx = 0;
    while(a) {
        mx = max(mx, a % 10);
        a /= 10;
    }
    return mx;
}

void solve() {
    int la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    if(ra - la >= 15 || rb - lb >= 15)  cout << 9 << '\n';
    else {
        int ans = 0;
        for(int i = la; i <= ra; i++) {
            for(int j = lb; j <= rb; j++){
                ans = max(ans, f(i + j));
            }
        }
        cout << ans << '\n';
    }
}

signed main() {
    cin.tie(0)->ios::sync_with_stdio(0);
    cout.tie(0);

    int t = 1;
#ifdef tests
    cin >> t;
#endif
    for(int _ = 1; _ <= t; _ ++) solve();
}