#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, s1;
  cin >> s;
  bool b = s.size() % 2 == 0;
  int k = s.size();
  for (int i = 0; i < k; i++) {
    if (b) {
      s1 = s[s.size() - 1] + s1;
      s.erase(s.size() - 1, 1);
    } else {
      s1 = s[0] + s1;
      s.erase(0, 1);
    }
    b = !b;
  }
  cout << s1 << endl;
  return 0;
}
