#include<bits/stdc++.h>

#define ll long long
#define mk make_pair
#define fi first
#define se second

using namespace std;

inline int read(){
    int x=0,f=1;char c=getchar();
    for(;(c<'0'||c>'9');c=getchar()){if(c=='-')f=-1;}
    for(;(c>='0'&&c<='9');c=getchar())x=x*10+(c&15);
    return x*f;
}

const int mod=998244353;
int ksm(int x,int y,int p=mod){
    int ans=1;
    for(int i=y;i;i>>=1,x=1ll*x*x%p)if(i&1)ans=1ll*ans*x%p;
    return ans%p;
}
int inv(int x,int p=mod){return ksm(x,p-2,p)%p;}
mt19937 rnd(time(0));
int randint(int l,int r){return rnd()%(r-l+1)+l;}
void add(int &x,int v){x+=v;if(x>=mod)x-=mod;}
void Mod(int &x){if(x>=mod)x-=mod;}
int cmod(int x){if(x>=mod)x-=mod;return x;}

void cmax(int &x,int v){x=max(x,v);}
void cmin(int &x,int v){x=min(x,v);}

signed main(void){

#ifndef ONLINE_JUDGE
    freopen("in.in","r",stdin);
#endif

    int tt=read();
    auto f=[&](int n){
        int mx=0;
        while(n)cmax(mx,n%10),n/=10;
        return mx;
    };
    while(tt--){
        int l=read(),r=read(),s=read(),t=read();
        if(r-l+1>=10&&t-s+1>=10)puts("9");
        else{
            int ans=0;
            for(int i=l;i<=r;i++)for(int j=s;j<=t;j++)cmax(ans,f(i+j));
            cout<<ans<<endl;
        }
    }

    return 0;
}