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