#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, step = 1;
  cin >> n;
  string t, s = "";
  cin >> t;
  for (int i = 0; i < n; i += s.size() + 1) {
    s += t[i];
  }
  cout << s;
  return 0;
}
