#include <iostream>

using namespace std;
typedef long long ll;

ll calc(ll x){
    ll ans = 0;
    while(x){
        ans = max(ans, x % 10);
        x /= 10;
    }
    return ans;
}

int main(){
    int t;
    cin >> t;

    while(t--){
        typedef long long ll;

        ll la, ra, lb, rb;
        cin >> la >> ra >> lb >> rb;

        ll ans = 0;
        for(ll a = la; a <= ra && ans < 9; ++a){
            for(ll b = lb; b <= rb && ans < 9; ++b){
                ans = max(ans, calc(a + b));
            }
        }
        cout << ans << "\n";
    }
}