#include <bits/stdc++.h>

int getmax(int x) {
    int ret = 0;
    while(x) {
        ret = std::max(ret, x % 10);
        x /= 10;
    }
    return ret;
}

void solve(){
    int a, b, c, d;
    std::cin >> a >> b >> c >> d;
    int res = 0;
    for (int i = a + c; i <= b + d; i += 1) {
        res = std::max(res, getmax(i));
        if (res == 9) break;
    }
    std::cout << res << "\n";
}

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    int T;
    std::cin >> T;
    while(T--) solve();    
    return 0;
}