#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string in, ans;
  cin >> in;
  int f = 0;
  for (unsigned i = 0; i < in.length(); i++) {
    ans += in[i];
    f++;
    i += f;
  }
  cout << ans;
  return 0;
}
