#include <iostream>
using namespace std;
#include <set>
#include <algorithm>
#include <cmath>
#include <map>
#include <cstdio>
#include <string>
#include <cstring>
#include <string.h>
#include <stdlib.h>
#include <iomanip>
#include <fstream>
#include <stdio.h>
#include <stack>
#include <queue>
#include <ctype.h>
#include <vector>
#define rep(i, a, n) for (int i = a; i <= n; i++)
#define per(i, a, n) for (int i = n; i >= a; i--)
#define pb emplace_back
#define pii pair<int, int>
#define ll long long
#define endl '\n'
int dir[4][2] =
    {
        {0, 1}, {0, -1}, {1, 0}, {-1, 0}};

ll fastpow(ll a, ll n, ll mod)
{
    ll ans = 1;
    a %= mod;
    while (n)
    {
        if (n & 1)
            ans = (ans * a) % mod;
        a = (a * a) % mod;
        n >>= 1;
    }
    return ans;
}

const int N = 1e5 + 10;
const double eps = 1e-8;

int main()
{
    ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//    freopen("ain.txt", "r", stdin);freopen("aout.txt", "w", stdout);
    int t;
    cin>>t;
    while(t--)
    {
        int ans=0;
        int la,ra,lb,rb;
        cin>>la>>ra>>lb>>rb;
        int leftt,rightt;
        leftt=la+lb;
        rightt=ra+rb;
        for(int i=leftt;i<=min(rightt,leftt+9);i++)
        {
            int temp=i;
            while(temp)
            {
                ans=max(ans,temp%10);
                temp/=10;
            }
        }
        cout<<ans<<endl;
    }
}