#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, s1 = "";
  int p, i, j;
  cin >> s;
  if (s.length() == 1)
    cout << s << endl;
  else if (s.length() % 2 != 0) {
    p = s.length() / 2;
    i = p - 1;
    j = p + 1;
    s1 = s1 + s[p];
    while (i >= 0 && j < s.length()) {
      s1 = s1 + s[j];
      s1 = s1 + s[i];
      j++;
      i--;
    }
    cout << s1 << endl;
  } else {
    p = s.length() / 2 - 1;
    i = p - 1;
    j = p + 1;
    s1 = s1 + s[p];
    while (i >= 0 && j < s.length()) {
      s1 = s1 + s[j];
      s1 = s1 + s[i];
      j++;
      i--;
    }
    s1 = s1 + s[j];
    cout << s1 << endl;
  }
}
