#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  vector<char> v;
  int i = 0, j = s.size() - 1;
  if (s.size() & 1) {
    cout << s[s.size() / 2];
    while (i < j) {
      v.push_back(s[i]);
      i++;
      v.push_back(s[j]);
      j--;
    }
    while (v.size() != 0) {
      cout << v.back();
      v.pop_back();
    }
    return 0;
  }
  while (i <= j) {
    v.push_back(s[j]);
    j--;
    v.push_back(s[i]);
    i++;
  }
  while (v.size() != 0) {
    cout << v.back();
    v.pop_back();
  }
}
