#include<bits/stdc++.h>
#define ll              long long 
#define all(v)          v.begin(),v.end()
#define ld              long double
#define pll             std::pair<ll,ll>
#define pi              std::pair<int,int>
#define vi              std::vector<int>
#define vll             std::vector<ll>
#define len(x)          (int)x.size()
#define vec(T)          std::vector<T>


template<typename T, typename = void>
struct is_printable : std::false_type {};

template<typename T>
struct is_printable<T, std::void_t<decltype(std::declval<std::ostream&>() << std::declval<T>())>> : std::true_type {};
template <typename T>
void print(const std::pair<T, T>& pair) {
    std::cout << "(" << pair.first << ", " << pair.second << ")";
}

// General print function
template <typename T>
void print(const T& val) {
    std::cout << val;
}

// Print function for std::vector
template <typename T>
void print(const std::vector<T>& vec) {
    std::cout << '[';
    int n = vec.size();
    for (int i = 0; i < n; i++) {
        print(vec[i]);
        if (i < n - 1) {
            std::cout << ",";
        }
    }
    std::cout << ']' << '\n';
}

// Variadic template print function
template<typename T, typename... Args>
void print(const T& t, const Args&... args) {
    print(t);
    std::cout << (is_printable<T>::value ? ' ' : '\0');
    print(args...);
    if (sizeof...(args) == 1 && is_printable<T>::value) std::cout << '\n';

}
template<class T, class U>
void chmin(T& a, const U& b) {if (a > b) a = b;}

int maxdigit(int x) {
    int res = 0;
    while (x) {
        res = std::max(res, x % 10);
        x /= 10;
    }
    return res;
}
void solve(){
    int la, ra, lb, rb;
    std::cin >> la >> ra >> lb >> rb;
    if (ra - la >= 10 || rb - lb >= 10) {
        std::cout << "9\n";
    }
    else {
        int ans = 0;
        for (int i = la; i <= ra; i++) {
            for (int j = lb; j <= rb; j++) {
                ans = std::max(ans, maxdigit(i + j));
            }
        }
        std::cout << ans << '\n';
    }

}
int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int t = 1;
    std::cin >> t;
    while (t--) solve();
}