#include <bits/stdc++.h>
using namespace std;
int f(int x) {
    int mx = 0;
    while(x) {
        mx = max(mx, x % 10);
        x /= 10;
    }
    return mx;
}
void Do() {
    int la, ra, lb, rb;
    cin >> la >> ra >> lb >> rb;
    int wt = 0;
    for(int i = la; i <= ra && i <= la + 50; ++ i) {
        for(int j = lb; j <= rb && j <= lb + 50; ++ j) {
            wt = max(wt, f(i + j));
        }
    }
    cout << wt << "\n";
}
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int T;
    cin >> T;
    while(T --) {
        Do();
    }
}