#include<bits/stdc++.h>
using namespace std;
int la,lb,ra,rb;
int calc(int x){
	int res=0;
	while(x){
		res=max(res,x%10);
		x/=10;
	}
	return res;
}
int read(){
	int x = 0, f = 1;
	char c = getchar();
	while(c < '0' || c > '9'){
		if(c == '-'){
			f = -1;
		}
		c = getchar();
	}
	while(c >= '0' && c <= '9'){
		x = x*10+c-'0';
		c = getchar();
	}
	return x*f;
}

void solve(){
	la=read(),ra=read(),lb=read(),rb=read();
	int l=la+lb,r=ra+rb;
	if(r-l+1>=10){
		printf("9\n");
	}
	else{
	//	cout<<l<<" "<<r<<endl;
		int ans=0;
		for(int i=l;i<=r;++i){
			ans=max(ans,calc(i)); 
		}
		printf("%d\n",ans);
	}
}
int main(){
	int T;
	cin>>T;
	while(T--){
		solve();
	}
}