#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  string t, s;
  getline(cin, t);
  s.resize(t.length());
  for (int i = (0); i < (t.length()); ++i) {
    if (i % 2 == 1)
      s[i] = t[(t.length() - 1) / 2 + (i + 1) / 2];
    else
      s[i] = t[(t.length() - 1) / 2 - i / 2];
  }
  cout << s;
  return 0;
}
