#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int i;
  cin >> s;
  int sz = s.size();
  if (sz <= 2)
    cout << s << endl;
  else if (sz == 3) {
    cout << s[1] << s[2] << s[0] << endl;
  } else {
    sz -= 2;
    if (sz % 2 == 1)
      sz = sz / 2 + 1;
    else
      sz = sz / 2;
    string s1 = "", s2 = "", res = "";
    for (i = 0; i < sz; i++) s1 += s[i];
    reverse(s1.begin(), s1.end());
    for (i = sz; i < s.size(); i++) s2 += s[i];
    res += s2[0];
    res += s2[1];
    res += s1[0];
    int k = 1;
    for (i = 2; i < s2.size(); i++) {
      res += s2[i];
      if (k <= s1.size() - 1) {
        res += s1[k];
        k++;
      }
    }
    cout << res << endl;
  }
  return 0;
}
