#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define ULL unsigned long long
#define Enter putchar('\n')
#define spc putchar(' ')
#define pb push_back
#define fi first
#define se second
inline void read(int &num){num=0;int f=1;char ch=getchar();while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){num=(num<<1)+(num<<3)+(ch^48);ch=getchar();}num*=f;}
inline void lread(long long &num){num=0;int f=1;char ch=getchar();while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){num=(num<<1)+(num<<3)+(ch^48);ch=getchar();}num*=f;}
void print(long long num){if(num<0){putchar('-');num=-num;}if(num>9){print(num/10);}putchar((num%10)^48);}
int f(int x){
    int d=0;
    while(x){
        d=max(d,x%10);
        x/=10;
    }
    return d;
}
int main(){
    int T,a,b,c,d;
    read(T);
    while(T--){
        read(a),read(b),read(c),read(d);
        if(b+d-a-c+1>=10){
            puts("9");
        }
        else{
            int ans=0;
            for(int i=a;i<=b;i++){
                for(int j=c;j<=d;j++){
                    ans=max(ans,f(i+j));
                }
            }
            print(ans),Enter;
        }
    }
    return 0;
}