#include <bits/stdc++.h>
using namespace std;
#define int long long
int check(int x,int y)
{
    int res=0;
    int cnt=x+y;
    while(cnt)
    {
        res=max(res,cnt%10);
        cnt/=10;
    }
    return res;
}
void solve()
{
    int l1,r1,l2,r2;
    cin>>l1>>r1>>l2>>r2;
    if(r1-l1>=10)
    {
        cout<<9<<endl;
        return ;
    }
    if(r2-l2>=10)
    {
        cout<<9<<endl;
        return ;
    }
    int ans=0;
    for(int i=l1;i<=r1;i++)
    {
        for(int j=l2;j<=r2;j++)
        {
            ans=max(ans,check(i,j));
        }
    }
    cout<<ans<<endl;

}
signed main()
{
    int T;
    cin>>T;
    while(T--)
    {
        solve();
    }
}