#include <bits/stdc++.h>
using namespace std;
template <typename T>
string to_str(T str) {
  stringstream stream;
  stream << str;
  return stream.str();
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  int n = s.length();
  int len = 0;
  if (n % 2 == 0)
    len = n / 2;
  else
    len = n / 2 + 1;
  string str = "";
  int i = len - 1;
  int j = len - 1;
  str += s[len - 1];
  while (j >= 0 or i < s.length()) {
    i++;
    j--;
    if (i < s.length()) str += s[i];
    if (j >= 0) str += s[j];
  }
  cout << str << endl;
  return 0;
}
