#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL MOD=1e9+7;
const LL INF=1e9;
int T,la,ra,lb,rb;
int f(int x)
{
    int ret=0;
    while (x)
    {
        ret=max(ret,x%10);
        x/=10;
    }
    return ret;
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    cin >> T;
    while (T--)
    {
        cin >> la >> ra >> lb >> rb;
        if (ra-la>=9 || rb-lb>=9) cout << 9 << '\n';
            else
            {
                int ans=0;
                for (int i=la;i<=ra;i++)
                    for (int j=lb;j<=rb;j++)
                        ans=max(ans,f(i+j));
                cout << ans << '\n';
            }
    }
    return 0;
}