#include<bits/stdc++.h>
#define int long long
using namespace std;
int T,a,b,c,d;
signed main(){
	cin>>T;
	while(T--){
		cin>>a>>b>>c>>d;
		if(b - a <= 10 && d - c <= 10){
			int ans = 0;
			for(int i = a + c; i <= b + d; i++){
				int x = i;
				int mx = 0;
				while(x){
					mx = max(mx,x % 10);
					x /= 10;
				}
				ans = max(ans,mx);
			}
			printf("%lld\n",ans);
		}
		else printf("9\n");
	}
	return 0;
}