#include <bits/stdc++.h>

using namespace std;

#define int long long
#define deg( x ) cout<<""#x"="<<x<<endl
#define endl '\n'
#define pll pair<int,int>
#define fr frist
#define se second

const int N=1e5+10;

int pan( int x ){
    int re=0;
    while( x ){
        re=max( re , x%10 );
        x/=10;
    }

    return re;
}

void solve( ){
    int la,ra,lb,rb;
    cin>>la>>ra>>lb>>rb;

    la+=lb , ra+=rb;

    int ans=0;
    for( int i=la; i<=min( ra , la+30 ); i++ ){
        ans=max( ans , pan( i ) );
    }

    cout<<ans<<endl;

}

signed main() {
    ios::sync_with_stdio( 0 );
    cin.tie( 0 ); cout.tie( 0 );

    int T=1;
    cin>>T;

    while( T-- ){
        solve(  );
    }

    return 0;
}