#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base ::sync_with_stdio(false);
  string s;
  cin >> s;
  int mid, i;
  int temp = 0;
  if (s.size() % 2 == 0) {
    temp = 1;
    mid = s.size() / 2 - 1;
  } else {
    mid = s.size() / 2;
  }
  cout << s[mid];
  for (i = 1; i <= mid; i++) {
    cout << s[mid + i] << s[mid - i];
  }
  if (temp) {
    cout << s[s.size() - 1] << endl;
  }
  return 0;
}
