#include <bits/stdc++.h>
using namespace std;
using ll = int64_t;
#define all(a) begin(a), end(a)
#define rep(i, s, e) for (int i = s; i < e; ++i)
#define asort(a) stable_sort(all(a))
#define rsort(a) stable_sort(rbegin(a), rend(a))
#define sum(a) reduce(all(a))
#define min_(a) reduce(all(a), *begin(a), [](auto x, auto y) { return min(x, y); })
#define max_(a) reduce(all(a), *begin(a), [](auto x, auto y) { return max(x, y); })
constexpr double degrees(double a) { return (a * 180.0) / M_PI; }
constexpr double radians(double a) { return (a * M_PI) / 180.0; }

int main(int, [[maybe_unused]] char *argv[]) {
#ifdef DEBUG
  freopen(argv[1], "r", stdin);
#endif

  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(15);

  int T, K;
  string S;
  cin >> T;
  while (T--) {
    cin >> K;
    cin >> S;

    string ans = string(min(K, (int)S.size()), S[0]);
    if ((int)S.size() > K) {
      decltype(S)::iterator it = S.end() - K;
      S.erase(it, S.end());
      ans += S;
    }
    cout << ans << endl;
  }
  return 0;
}