#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
class {
 public:
  void solve() {
    string s;
    int n;
    cin >> n;
    cin >> s;
    s = "#" + s;
    string ret;
    for (int i = 1, j = 1; i < s.length(); i += j, j++) ret += s[i];
    cout << ret;
  }
} NSPACE;
int main() {
  ios_base::sync_with_stdio(false);
  cout.tie(0);
  cin.tie(0);
  NSPACE.solve();
}
