#include <bits/stdc++.h>
using namespace std;
int main() {
  string t, s;
  cin >> t;
  int pos = (t.length() / 2) + (t.length() % 2) - 1;
  s = t[pos];
  int offs = 1;
  bool rwise = true;
  while (s.length() < t.length()) {
    if (rwise) {
      s = s + string(1, t[pos + offs]);
      rwise = false;
    } else {
      s = s + string(1, t[pos - offs]);
      rwise = true;
      offs++;
    }
  }
  cout << s << endl;
  return 0;
}
