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