#include <bits/stdc++.h>
#define int long long
using namespace std;
int f(int x) {
    int ma=0;
    while(x) {
        ma=max(ma,x%10);
        x/=10;
    }
    return ma;
}
void solve() {
    int la,ra,lb,rb;
    cin>>la>>ra>>lb>>rb;
    if(ra-la>20||lb-rb>20) {
        cout<<"9\n";
        return;
    }
    int ans=0;
    for(int x=la;x<=ra;++x) {
        for(int y=lb;y<=rb;++y) {
            ans=max(ans,f(x+y));
        }
    }
    cout<<ans<<"\n";
}
signed main() {
    int t;
    cin>>t;
    while(t--) solve();
    return 0;
}