#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int l = (s.length() - 1) / 2;
  cout << s[l];
  int lf = l - 1, rf = l + 1;
  for (int i = 0; i < (s.length() - 1) / 2; ++i) {
    cout << s[rf++] << s[lf--];
  }
  if (rf < s.length()) cout << s[rf];
  if (lf > 0) cout << s[lf];
}
