#include <bits/stdc++.h>
#define int long long
using namespace std;
void solve();
signed main(){
	cin.sync_with_stdio(0);
	cin.tie(0);
	int T = 1;
	cin >> T;
	while(T--){
		solve();
	}
	return 0;
}
void solve(){
	int l1, r1, l2, r2;
	cin >> l1 >> r1 >> l2 >> r2;
	int l = l1 + l2;
	int r = r1 + r2;
	int d = r - l + 1;
	if(d > 100){
		cout << "9\n";
	}
	else{
		int ans = 0;
		for(int i = l;i <= r;i++){
			int x = i;
			while(x){
				ans = max(ans, x % 10);
				x /= 10;
			}
		}
		cout << ans << "\n";
	}
}