#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;

int T;
int get(int x)
{
    int ans=0;
    while(x) ans=max(ans,x%10), x/=10;
    return ans;
}
int main()
{
    // freopen("testdata.in","r",stdin);
    cin >> T;
    while(T--)
    {
        int la, ra, lb, rb;
        cin >> la >> ra >> lb >> rb;
        if(ra-la>=10||rb-lb>=10) cout << "9\n";
        else
        {
            int ans=0;
            for(int i=la;i<=ra;i++)
            {
                for(int j=lb;j<=rb;j++)
                {
                    ans=max(ans,get(i+j));
                }
            }
            cout << ans << '\n';
        }
    }
    return (0-0);
}