#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  char s;
  int d = 1, j = 1;
  for (int i = 1; i <= n; i++) {
    cin >> s;
    j -= 1;
    if (j == 0) {
      cout << s;
      d += 1;
      j = d;
    }
  }
  return 0;
}
