#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int i = 1, j = 1, m = s.length(), p = 0;
  char ans[s.length()];
  if (m != 1) {
    if (m % 2 == 0) {
      m /= 2;
      ans[0] = s[m - 1];
      cout << ans[0];
      for (int k = 1; s[k] != '\0'; k++) {
        if (p == 0) {
          ans[k] = s[m + j - 1];
          p = 1;
          j++;
        } else {
          ans[k] = s[m - i - 1];
          p = 0;
          i++;
        }
        cout << ans[k];
      }
    } else {
      m /= 2;
      ans[0] = s[m];
      cout << ans[0];
      for (int k = 1; s[k] != '\0'; k++) {
        if (p == 0) {
          ans[k] = s[m + j];
          p = 1;
          j++;
        } else {
          ans[k] = s[m - i];
          p = 0;
          i++;
        }
        cout << ans[k];
      }
    }
    cout << "\n";
  } else
    cout << s << "\n";
}
