#include <bits/stdc++.h>
using namespace std;
int half(string s) {
  return s.size() % 2 == 0 ? (s.size() / 2) - 1 : (s.size() / 2);
}
void solve(string s) {
  int i = 0, j = 0, size = s.size();
  bool right = false;
  cout << s[half(s)];
  size--;
  string ss;
  while (size != 0) {
    if (!right) {
      i++;
      ss += s[half(s) + i];
      right = true;
    } else {
      j++;
      ss += s[half(s) - j];
      right = false;
    }
    size--;
  }
  cout << ss;
}
int main() {
  string s;
  cin >> s;
  solve(s);
}
