#include <bits/stdc++.h>
#define rep(a,b,c) for(int a=(b);a<=(c);a++)
#define per(a,b,c) for(int a=(b);a>=(c);a--)
#define vi vector<int>
#define pb push_back
#define ll long long
#define mem(a,b) memset(a,b,sizeof(a))
using namespace std;

template<class T>inline void read(T &x) {
	T f=1; x=0; char s=getchar();
	while(s<'0'||s>'9'){if(s=='-')f=-1;s=getchar();}
	while(s>='0'&&s<='9'){x=x*10+s-'0';s=getchar();}
	x*=f;
}

inline int calc(int x) {
	int ans=0;
	while(x) {
		ans=max(ans,x%10);
		x/=10;
	}
	return ans;
}

int la,ra,lb,rb;

inline void solve() {
	read(la); read(ra); read(lb); read(rb);
	if(max(ra-la+1,rb-lb+1)>=10) {
		puts("9");
		return;
	}
	int ans=0;
	rep(i,la,ra) rep(j,lb,rb) ans=max(ans,calc(i+j));
	printf("%d\n",ans);
}

int main() {
	int T; read(T); while(T--)
	solve();
}