#include <bits/stdc++.h>
using namespace std;
using ll = long long;
string a = "Valdik";
string b = "Valera";
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  string s;
  cin >> s;
  int n = s.length();
  int mid = s.length() / 2 - (n % 2 == 1 ? 0 : 1);
  string ans = string(1, s[mid]);
  cerr << "MID: " << mid << " LEN: " << n << endl;
  cerr << "ANS: " << ans << endl;
  int i = 1;
  while (mid + i < n || mid - i > 0) {
    if (mid + i < n) ans += s[mid + i];
    if (mid - i >= 0) ans += s[mid - i];
    ++i;
  }
  cout << ans << endl;
  return 0;
}
