/* Code by pp_orange */
//#pragma GCC optimize(2)
#include<bits/stdc++.h>
#define m_p(a,b) make_pair(a,b)
#define pb push_back
#define ll long long
#define ull unsigned long long
#define ld long double
#define inf 0x7FFFFFFF
#define inff 9223372036854775807
#define rep(i,l,r) for(int i=l;i<r;++i)
#define repp(i,l,r) for(int i=l;i<=r;++i)
#define per(i,r,l) for(int i=r-1;i>=l;--i)
#define pper(i,r,l) for(int i=r;i>=l;--i)
#define pii pair<int,int>
#define fi first
#define se second
#define p_q priority_queue
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define ls(x) ((x)<<1)
#define rs(x) ((x)<<1|1)
#define lb(x) ((x)&-(x))
#define lg(x) (31^__builtin_clz(x))
const int mod = 998244353;
//#define int ll
using namespace std;
inline int rd(){
	int x(0),f(1);char ch=getchar();
	while(!isdigit(ch)){if(ch=='-')f=-f;ch=getchar();}
	while (isdigit(ch)){x=(x<<3)+(x<<1)+(ch^48);ch=getchar();}
	return x*f;
}
inline void out(int X){
	if(X<0) {X=~(X-1); putchar('-');}
	if(X>9) out(X/10);
	putchar(X%10+'0');
}
ll pw(ll x,int d){
	ll t = 1;
	for(;d;d>>=1,x=x*x%mod)if(d&1)t = t*x%mod;
	return t;
}
#define MAX 200005
signed main(){
	//freopen("in.in","r",stdin);
	//freopen("out.out","w",stdout);
	int T = rd();
	while(T--){
		int la = rd();
		int ra = rd();
		int lb = rd();
		int rb = rd();
		if(ra-la>=10||rb-lb>=10){cout<<9<<endl;}
		else{
			int ans = 0;
			repp(i,la,ra){
				repp(j,lb,rb){
					int x = i+j;
					int mx = 0;
				//	cout<<":"<<x<<endl;
					while(x){
						mx = max(mx,x%10);
						x /= 10;
					}
					ans = max(mx,ans);
				}
			}
			cout<<ans<<endl;
		}
	}
	return 0;
}