#include <bits/stdc++.h>
#define IOS ios::sync_with_stdio(0), cin.tie(0)
#define int long long
#define endl '\n'
#define lowbit(x) (x)&(-x)
#define pii pair<int,int>
#define all(s) s.begin(), s.end()
#define ls(x) (x<<1)
#define rs(x) (x<<1|1) 
#define here system("pause")
using namespace std;
template <class T> inline void read(T& x) { x = 0; char c = getchar(); bool f = 0; for (; !isdigit(c); c = getchar()) f ^= (c == '-'); for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + (c ^ 48); x = f ? -x : x; }
template <class T> inline void write(T x) { if (x < 0) putchar('-'), x = -x; if (x < 10) putchar(x + 48); else write(x / 10), putchar(x % 10 + 48); }

const int N = 5e5+5;
const int mod = 998244353;
const int INF = 1e15+7;
const double eps = 1e-4;
inline int pow(int a, int b, int p){ int res = 1%p; while(b){ if(b&1) res=res*a%p; a=a*a%p, b>>=1;} return res;}
inline int inv(int a, int p){ return pow(a,p-2,p)%p;}
using namespace std;

inline int work(int x, int y){
	int res = 0, sum = x+y;
	while(sum){
		res = max(res, sum%10);
		sum/=10;
	}
	return res;
}
inline void sol(){
	int l, r, x, y;
	cin >> l >> r >> x >> y;
	if(r-l>=10 || y-x>=10){
		cout << 9 << endl;
	}else{
		int mx = 0;
		for(int i=l;i<=r;i++){
			for(int j=x;j<=y;j++){
				mx = max(mx, work(i, j));
			}
		}
		cout << mx << endl;
	}
}

signed main(){
	IOS;
	int tc = 1;
	cin >> tc;
	while(tc--){
		sol();
	}
	return 0;
}