#include <bits/stdc++.h>
using namespace std;
int main() {
  string a;
  cin >> a;
  int n = a.size();
  deque<char> s, ans;
  for (int i = 0; i < n; ++i) s.push_back(a[i]);
  while (!s.empty()) {
    if (n % 2 == 0) {
      ans.push_front(s.back());
      s.pop_back();
    } else {
      ans.push_front(s.front());
      s.pop_front();
    }
    n--;
  }
  for (int i = 0; i < ans.size(); ++i) cout << ans[i];
  return 0;
}
