#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, l, c = 0;
  string str, res = "";
  cin >> str;
  l = str.length();
  x = (l - 1) / 2;
  while (str.length() != 0) {
    res.append(str.begin() + x, str.begin() + (x + 1));
    str.erase(str.begin() + x);
    if (c % 2 == 0)
      c++;
    else {
      c++;
      x--;
    }
  }
  cout << res << endl;
  return 0;
}
