#include<bits/stdc++.h>
#if __has_include(<atcoder/all>)
#endif
using namespace std;
#define done(...) return pp(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;lin(__VA_ARGS__)
#define STRING(...) string __VA_ARGS__;lin(__VA_ARGS__)
#define FO(n) for(ll IJK=n;IJK-->0;)
#define defpp template<ostream&o=cout>void pp(const auto&...a){[[maybe_unused]]const char*c="";((o<<c<<a,c=" "),...);o<<'\n';}void epp(const auto&...a){pp<cerr>(a...);}
#define entry defpp void main();void main2();}int main(){my::io();my::main();}namespace my{
#define multiple_testcases LL(T);FO(T)main2();}void main2(){
namespace my{
void io(){cin.tie(nullptr)->sync_with_stdio(0);cout<<fixed<<setprecision(15);}
using ll=long long;
void lin(auto&...a){(cin>>...>>a);}
}
namespace my{entry
void main(){
  multiple_testcases
  LL(K);
  STRING(s);
  if(K>=s.size())done(string(s.size(),s[0]));
  pp(string(K,s[0])+s.substr(0,s.size()-K));
}}