#include <bits/stdc++.h>
using namespace std;
const long double PI = 4 * atan(1);
void solve() {
  string s;
  cin >> s;
  int n = s.length();
  string res = "";
  int mid = (n + 1) / 2 - 1;
  res += s[mid];
  for (int i = 1; i <= mid; i++) {
    res += s[mid + i];
    res += s[mid - i];
  }
  if (n % 2 == 0) {
    res += s[n - 1];
  }
  cout << res << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(0);
  solve();
  return 0;
}
