#include<bits/stdc++.h>
#define int long long

using namespace std;

const int N = 1e6 + 5;
const int mod = 1e9 + 7;
const int MAX_VAL = 1e15+5;

int n, m, k, l, i, j, a, b, r, x, y;
int d[N], sum[N];
int pr[N];
int res, tot, ans;

int get(int n){
    int ret=0;
    while(n>0){
        ret=max(ret, n%10);
        n/=10;
    }
    return ret;
}

void solve(){
    cin>>l>>r>>a>>b;
    int res =0;
    if(r-l+b-a+1 >= 10){
        cout<<9<<endl;
        return;
    } else {
        for(int i=l;i<=r;i++){
            for(int j=a;j<=b;j++){
                res=max(res, get(i+j));
            }
        }
    }
    cout<<res<<endl;
}


signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr);
    int t=1;
    cin>>t;

    while(t--){
        solve();
    }

}