#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int t;
  cin >> t;
  while (t--) {
    int k;
    string s;
    cin >> k >> s;
    rep(i, s.size()) cout << s[max(0, i - k)];
    cout << '\n';
  }
  return 0;
}