#include <bits/stdc++.h>
using namespace std;
#define rep(i, x, y) for (int i = (x); i <= (y); i++)
#define per(i, x, y) for (int i = (x); i >= (y); i--) 
// #define int long long
using ll = long long; using ull = unsigned long long;
inline int read() {
    char ch = getchar(); int s = 0, f = 1;
    while (!isdigit(ch)) {if (ch == '-') f = -1; ch = getchar();}
    while (isdigit(ch)) s = (s << 1) + (s << 3) + (ch ^ 48), ch = getchar();
    return s * f;
}
int la, ra, lb, rb;
inline void sol() {
    la = read(), ra = read(), lb = read(), rb = read();
    int a = 0, b = 0;
    if (ra - la >= 9 || rb - lb >= 9) {
        cout << 9 << '\n';
        return ;
    }
    rep (j, la, ra)
        rep (i, lb, rb) {
            int x = i + j;
            while (x) {
                b = max(b, x % 10);
                x /= 10;
            }
        }
    cout << b << '\n';
}
signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int _ = read(); while (_--) sol();
    return 0;   
}