#include<iostream>
#include<cstring>
#include<vector>
using namespace std;
using LL = long long;

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    int T;
    cin >> T;
    while(T--){
        int l1, r1, l2, r2;
        cin >> l1 >> r1 >> l2 >> r2;
        if (r1 - l1 + 1 >= 10 || r2 - l2 + 1 >= 10){
            cout << 9 << '\n';
            continue;
        }
        int mx = 0;
        for(int i = l1; i <= r1; i++){
            for(int j = l2; j <= r2; j++){
                int x = i + j;
                while(x){
                    mx = max(mx, x % 10);
                    x /= 10;
                }
            }
        }
        cout << mx << '\n';
    }

}