#include <bits/stdc++.h>
using i64 = long long;

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