#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n = 0, m = 0, a = 0, b = 0;
  string s;
  cin >> s;
  string t;
  vector<char> q;
  n = s.size();
  if (n == 2) {
    cout << s << endl;
    return 0;
  }
  m = n / 2;
  a = 0;
  if (n % 2 != 0) {
    m = (n - 1) / 2;
    t[0] = s[m];
    q.push_back(s[m]);
    for (long long i = 1; i < n; i += 2) {
      a++;
      q.push_back(s[m + a]);
      q.push_back(s[m - a]);
    }
  } else {
    m = (n - 1) / 2;
    q.push_back(s[m]);
    for (long long i = 1; i < n - 1; i++) {
      a++;
      if (m + a <= n - 1) {
        q.push_back(s[m + a]);
      }
      if (m - a >= 0) {
        q.push_back(s[m - a]);
      }
    }
  }
  for (long long i = 0; i < q.size(); i++) {
    cout << q[i];
  }
}
