#include <bits/stdc++.h>
#define endl '\n'
#define int long long
#define gcd __gcd
using namespace std;
typedef pair<int,int> pii;
const int INF = 9e18;
const int inf = 2e9;

signed main()
{
    // ios::sync_with_stdio(0);
    // cin.tie(0);
    int t;
    cin >> t;
    while(t --)
    {
        int l1,r1,l,r;
        cin >> l1 >> r1 >> l >> r;
        int fi = -1,se = -1;
        int mi = l1 + l;
        int ma = r1 + r;
        int ans = 0 ;
        if(ma - mi + 1 >= 10) ans = 9;
        else for(int i = mi;i <= ma;i ++)
        {
            int now = i;
            while(now)
            {
                ans = max(ans,now % 10);
                now /= 10;
            }
        }
        cout << ans << endl;
    }
}