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