// Homura Akemi a.k.a. Starrykiller (/user/235125)
// I love Madoka Kaname forever! 
#include <bits/stdc++.h>

using namespace std;

template<typename L, typename R>
auto range(L l, R r) { return views::iota(l,r); }
auto rev=views::reverse;

template<typename T>
_GLIBCXX_ALWAYS_INLINE void chmax(T &a, T b) { a=max(a,b); }
template<typename T>
_GLIBCXX_ALWAYS_INLINE void chmin(T &a, T b) { a=min(a,b); }
#define int long long

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
int T; cin>>T;
// int T=1;
while (T--) []{
    int a, b, c, d;
    cin>>a>>b>>c>>d;
    auto f=[](int x) {
        int ans=0;
        while (x) chmax(ans,x%10), x/=10;
        return ans;
    };
    int ans=0;
    for (int i=a; i<=min(b,a+10); ++i)
    for (int j=c; j<=min(d,c+10); ++j)
    chmax(ans,f(i+j));
    cout<<ans<<'\n';
}();
}