#include <bits/stdc++.h>
using namespace std;
string s;
int a, b, n;
int main() {
  cin >> s;
  n = s.length();
  if (n & 1) {
    a = n / 2;
    b = n / 2 + 1;
  } else {
    a = n / 2 - 1;
    b = n / 2;
  }
  for (; a >= 0 && b < n;) {
    cout << s[a];
    a--;
    cout << s[b];
    b++;
  }
  if (n & 1) cout << s[0];
  cout << endl;
  return 0;
}
