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