#include <bits/stdc++.h>
#define inf 0x3f3f3f3f
#define int long long
#define PII pair<int,int>
#define IOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)
using namespace std;
const int N = 2e5 + 10;

void solve(){
    int la, ra, lb, rb;  cin >> la >> ra >> lb >> rb;
    int l = la + lb, r = ra + rb;
    int ans = 0;
    for(int i = l, cnt = 0; i <= r && cnt <= 10; i ++, cnt ++){
        string s = to_string(i);
        for(int j = 0; j < s.size(); j ++){
            ans = max(ans, (int)(s[j] - '0'));
        }
    }
    cout << ans << endl;
    
    
}

signed main() {
//	IOS;
    int t;  cin >> t;
    while(t --){
        solve();
    }
    
    return 0;
}