#include <bits/stdc++.h>
using namespace std;
string gs(char x) {
  string s(1, x);
  return (s);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int T = 1;
  while (T-- > 0) {
    string t;
    cin >> t;
    int n = t.length();
    int mid = (n - 1) / 2;
    string s = gs(t[mid]);
    for (int i = 1; i <= mid; ++i) {
      s = s + gs(t[mid + i]);
      s = s + gs(t[mid - i]);
    }
    if (n % 2 == 0) s = s + gs(t[n - 1]);
    cout << s;
    cout << '\n';
  }
  return 0;
}
