#include<bits/stdc++.h>
#define F(i, a, b) for(int i = a; i <= b; i ++)
#define int long long
using namespace std;

int n;

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

void sol() {
    int la, ra, lb, rb; cin >> la >> ra >> lb >> rb;
    int res = 0;
    F(i, la, min(ra, la + 10)) F(j, lb, min(rb, lb + 10)) res = max(res, cal(i + j));
    cout << res << "\n";
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t; cin >> t;
    F(i, 1, t) sol();
    return 0;
}