#include <bits/stdc++.h>
using namespace std;
deque<char> ans;
int main() {
  string s;
  cin >> s;
  if (s.size() % 2 == 0) {
    int t = s.size() / 2 - 1;
    ans.push_back(s[t]);
    for (int i = 1; i < s.size() / 2; ++i) {
      ans.push_back(s[t + i]);
      ans.push_back(s[t - i]);
    }
    ans.push_back(s[s.size() - 1]);
  } else {
    int t = s.size() / 2;
    ans.push_back(s[t]);
    for (int i = 1; i <= t; ++i) {
      ans.push_back(s[t + i]);
      ans.push_back(s[t - i]);
    }
  }
  for (int i = 0; i < ans.size(); ++i) {
    cout << ans[i];
  }
}
