#include<iostream>
#include<bits/stdc++.h>
using namespace std;
#define int long long
void solve(){
    int a, b, c, d;
    cin>>a>>b>>c>>d;
    a = a + c, b = b + d;
    int ans = 0;
    auto get = [&](int x) -> int
    {
        int maxx = 0;
        while(x)
        {
            maxx=max(maxx,(int)x%10);
            x /= 10;
        }
        return maxx;
    };
    for (int i = 1; i <= b - a;i++){
        ans = max(ans, (i+a%10) % 10);
    }
    cout << max(max(get(a), get(b)), ans) << endl;
} 
signed main(){
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t;
    cin>>t;
    while(t--){
        solve();
    }
}