#include <bits/stdc++.h>
#define inf 1000000007
#define mod 1000000007
// #define int long long
// #pragma GCC optimize("Ofast","inline","-ffast-math")
// #pragma GCC target("avx,sse2,sse3,sse4,mmx")
using namespace std;
template <typename T> void read(T &x){
	x=0;char ch=getchar();int fh=1;
	while (ch<'0'||ch>'9'){if (ch=='-')fh=-1;ch=getchar();}
	while (ch>='0'&&ch<='9')x=x*10+ch-'0',ch=getchar();
	x*=fh;
}
template <typename T> void write(T x) {
	if (x<0) x=-x,putchar('-');
	if (x>9) write(x/10);
	putchar(x%10+'0');
}
template <typename T> void writeln(T x) {
	write(x);
	puts("");
}
signed main()
{
	// freopen(".in","r",stdin);
	// freopen(".out","w",stdout);
	int tc;read(tc);
	while(tc--)
	{
		int la,ra,lb,rb;
		read(la);read(ra);read(lb);read(rb);
		if(ra-la+1>=10||rb-lb+1>=10) {puts("9");continue;}
		int mx=0;
		for(int a=la;a<=ra;++a)
			for(int b=lb;b<=rb;++b)
			{
				int c=a+b;
				int d=0;
				while(c)
				{
					d=max(d,c%10);
					c/=10;
				}
				mx=max(mx,d);
			}
		writeln(mx);
	}
	return 0;
}