#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  string s1 = s;
  int l = s.size();
  int i = 0;
  if (l == 1 || l == 2) {
    cout << s << endl;
    return 0;
  }
  if (l % 2 == 0) {
    while (l > 0) {
      s1[i] = s[l / 2 - 1];
      s1[i + 1] = s[l / 2];
      i += 2;
      s.erase(s.begin() + l / 2 - 1, s.begin() + l / 2 + 1);
      l -= 2;
      s.resize(l);
    }
  } else {
    while (l > 0) {
      s1[i] = s[l / 2];
      s1[i + 1] = s[l / 2 + 1];
      i += 2;
      s.erase(s.begin() + l / 2, s.begin() + l / 2 + 2);
      l -= 2;
      s.resize(l);
      if (l == 1) {
        s1[i] = s[l - 1];
        break;
      }
    }
  }
  cout << s1 << endl;
  return 0;
}
