#include <bits/stdc++.h>
using namespace std;
int A[300001];
vector<int> v;
int main() {
  string t, s;
  int pre, post, index;
  cin >> t;
  int d = t.size();
  if (d == 1) {
    cout << t << endl;
    return 0;
  }
  if (d % 2 == 0)
    index = d / 2 - 1;
  else
    index = d / 2;
  s += t[index];
  pre = index;
  post = index;
  while (1) {
    post = post + 1;
    pre = pre - 1;
    s += t[post];
    if (pre >= 0) s += t[pre];
    if (s.size() == t.size()) break;
  }
  cout << s << endl;
  return 0;
}
