#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
const int MOD = 1e9;
const int N = 1e6 + 5;
const ll oo = 9e18;
const int M = 501;
void solve() {
  string s;
  cin >> s;
  string ans = "";
  if ((int)s.size() % 2) {
    ans += s[(int)s.size() / 2], s.erase(s.begin() + (int)s.size() / 2);
    while ((int)s.size()) {
      int x = (int)s.size() / 2;
      int y = (int)s.size() / 2 - 1;
      ans += s[x];
      ans += s[y];
      s.erase(s.begin() + y);
      s.erase(s.begin() + y);
    }
  } else {
    while ((int)s.size()) {
      int x = (int)s.size() / 2;
      int y = (int)s.size() / 2 - 1;
      ans += s[y];
      ans += s[x];
      s.erase(s.begin() + y);
      s.erase(s.begin() + y);
    }
  }
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) solve();
}
