#include<bits/stdc++.h>
using namespace std;
bool compare(string x,string y){
return (x>y);
}
int main() {
int t;
cin>>t;
while(t--){
int n;
cin>>n;
string a[n];
for(int i=0;i<n;i++){
cin>>a[i];
}
sort (a,a+n,compare);
for (int i=0;i<n;i++){
cout<<a[i];
}
cout<<'\n';
}
return 0;
}
Ans is correct, yet all testcases fail...