#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s, a = "";
  cin >> s;
  int j = 1, k = 2;
  for (int i = 0; i < s.size(); i++) {
    if (i == j - 1) a += s[i], j += k, k++;
  }
  cout << a;
  return 0;
}
