#include <bits/stdc++.h>
using namespace std;
template <typename Arg1>
void pn(Arg1&& arg1) {
  cout << arg1 << "\n";
}
template <typename Arg1, typename... Args>
void pn(Arg1&& arg1, Args&&... args) {
  cout << arg1 << "\n";
  pn(args...);
}
template <typename Arg1>
void ps(Arg1&& arg1) {
  cout << arg1 << " ";
}
template <typename Arg1, typename... Args>
void ps(Arg1&& arg1, Args&&... args) {
  cout << arg1 << " ";
  ps(args...);
}
template <typename Arg1>
void pvs(Arg1&& arg1, long long n) {
  for (long long i = 0; i < n; i++) ps(arg1[i]);
}
template <typename Arg1>
void pvn(Arg1&& arg1, long long n) {
  for (long long i = 0; i < n; i++) pn(arg1[i]);
}
template <typename Arg1>
void bug(Arg1&& arg1) {
  cout << "->" << arg1 << endl;
}
void solve() {
  long long y, z, n, p, x, k, l, sum = 0, flag = 0, t, ans = 0;
  string s, s1 = "", s2;
  cin >> n;
  cin >> s;
  for (long long i = 0; i < s.length(); i++) {
    s1 += s[i++];
  }
  pn(s1);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int test = 1, i = 1;
  cin >> test;
  while (test--) {
    solve();
  }
  return 0;
}
