#include <bits/stdc++.h>
using namespace std;
void solve() {
  string s, str = "";
  cin >> s;
  if (s.size() < 3) {
    cout << s;
    return;
  }
  int i = 0, flag = 0, t = 0, c = 0;
  while (1) {
    t = 0;
    if ((s.size() % 2 || flag > 1) && c < s.size()) {
      str += string(1, s[i]);
      flag = 2;
      c++;
      t = 1;
    }
    if (s.size() % 2 == 0 && flag == 2) i++;
    if ((s.size() % 2 == 0 || flag > 1) && c < s.size()) {
      str += string(1, s[s.size() - 1 - i]);
      flag = 2;
      c++;
      t = 1;
    }
    if (s.size() % 2) i++;
    if (!t) break;
  }
  reverse(str.begin(), str.end());
  cout << str;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
