#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  char arr[100];
  int n;
  string res = "";
  cin >> n;
  int k = 0;
  for (int i = 1; i <= n; i++) cin >> arr[i];
  for (int i = 1; i <= n; i++) {
    if (k >= n) break;
    res += arr[k + i];
    k += i;
  }
  cout << res << endl;
}
