#include<bits/stdc++.h>
using namespace std;
int T,la,lb,ra,rb;
int cal(int x){
    int res = 0;
    while(x){
        res = max(res, x % 10);
        x /= 10;
    }
    return res;
}
int main(){
    scanf("%d",&T);
    while(T--){
        scanf("%d %d %d %d",&la,&ra,&lb,&rb);
        if(ra - la + 1 >= 10 || rb - lb + 1 >= 10){
            puts("9");
            continue;
        }
        int ans = 0;
        for(int i = la; i <= ra; i++) for(int j = lb; j <= rb; j++) ans = max(ans,cal(i + j));
        printf("%d\n",ans);
    }
}