#include <bits/stdc++.h>
using namespace std;
const int Z = (int)3e3 + 111;
const int N = (int)1e6 + 111;
const int INF = (int)1e9 + 111;
const int MOD = (int)1e9 + 7;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string t, ans;
  cin >> t;
  int k;
  if (t.size() % 2)
    k = 1;
  else
    k = 0;
  int po1(0), po2(t.size() - 1);
  while (ans.size() != t.size()) {
    if (k) {
      ans = t[po1] + ans;
      po1++;
    } else {
      ans = t[po2] + ans;
      po2--;
    }
    k = !k;
  }
  cout << ans;
  return 0;
}
