#include<bits/stdc++.h>
#define LL long long
#define len(G) (LL)(G).size()
using namespace std;
LL la,ra,lb,rb;
template<typename T>
inline void read(T &x)
{
	x=0;int w=1;char c=getchar();
	while(!isdigit(c)){if(c=='-')w=-1;	c=getchar();}
	while(isdigit(c)){x=x*10+(c-'0');	c=getchar();}
	if(w==-1)	x=-x;
}
template<typename T,typename ...Args>
inline void read(T &x,Args &...args)
{
	read(x),read(args...);
}
LL f(LL x)
{
	LL ans=0;
	while(x)
	{
		ans=max(ans,x%10);
		x/=10;
	}
	return ans;
}
void solve()
{
	read(la,ra,lb,rb);
	if(ra-la+1>=10||rb-lb+1>=10)
	{
		puts("9");
		return;
	}
	LL ans=0;
	for(LL i=la;i<=ra;++i)
		for(LL j=lb;j<=rb;++j)
			ans=max(ans,f(i+j));
	printf("%lld\n",ans);
}
int main()
{
	LL T;
	read(T);
	while(T--)	solve();
	return 0;
}