#include <bits/stdc++.h>
using namespace std;
signed main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  string ans;
  int col = 0;
  for (int i = 0; i < s.size(); i++) {
    ans += s[i];
    i += col;
    col++;
  }
  cout << ans;
  return 0;
}
