#include<bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t;
    cin >> t;
    while( t-- ){
        int la,ra,lb,rb;
        cin >> la >> ra >> lb >> rb;
        int ans = 0;
        int cnt = 0;
        for (int i = la; i <= ra; ++i) {
            for(int j = lb;j <= rb; ++j){
                int c = i+j;
                while(c){
                    ans = max(ans,c%10);
                    c /= 10;
                }
                cnt++;
                if( cnt > 1000 )break;
            }
            if( cnt > 1000 )break;
        }
        cout << ans << endl;
    }
    return 0;
}