#include<bits/stdc++.h>
using namespace std;
#define int long long

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

void prepare(){
    int a,b,c,d;
    cin >> a >> b >> c >> d;
    int ans = 0;
    for(int i = a; i <= min(b, a + 10); i++){
        for(int j = c; j <= min(d, c + 10); j++){
            ans = max(ans, check(i + j));
        }
    }
    cout << ans << "\n";
}

signed main(){
    ios::sync_with_stdio(false);
    int T;
    cin >> T;
    while(T--){
        prepare();
    }
}