#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int n = s.size();
  int p;
  if (n % 2 == 0)
    p = n / 2 - 1;
  else
    p = n / 2;
  string res = "";
  res += s[p];
  int p1 = p - 1;
  int p2 = p + 1;
  while (p2 < n) {
    res += s[p2];
    if (p1 >= 0) res += s[p1];
    p2++;
    p1--;
  }
  cout << res << endl;
}
