#include<iostream>
#include<cstdio>
using namespace std;
int read()
{
	char c=0;
	int sum=0;
	while (c<'0'||c>'9') c=getchar();
	while ('0'<=c&&c<='9') sum=sum*10+c-'0',c=getchar();
	return sum;
}
int T,la,ra,lb,rb,l,r,ans;
int F(int x)
{
	if (!x) return 0;
	return max(F(x/10),x%10);
}
int main()
{
	T=read();
	while (T--)
	{
		la=read(),ra=read(),lb=read(),rb=read(),l=la+lb,r=ra+rb;
		if (r-l+1>=10) puts("9");
		else
		{
			ans=0;
			for (int i=l;i<=r;++i) ans=max(ans,F(i));
			printf("%d\n",ans);
		}
	}
	return 0;
}