#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;
using ll=long long;
using pii=pair<int,int>;
using vi=vector<int>;
using vl=vector<ll>;
#define pb push_back
#define all(a) begin(a),end(a)

const int N=300010,MOD=1e9+7;
const char en='\n';
const ll LLINF=1ll<<60;

int t;

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin>>t;
	while (t--)
	{
		ll l1,r1,l2,r2;
		cin>>l1>>r1>>l2>>r2;
		ll l=l1+l2,r=r1+r2;
		int ma=0;
		for (ll x=l;x<=r;++x)
		{
			ll y=x;
			while (y)
			{
				ma=max(ma,int(y%10));
				y/=10;
			}
			if (ma==9) break;
		}
		cout<<ma<<en;
	}
}