#include <bits/stdc++.h>
using namespace std;
int main() {
  string t;
  cin >> t;
  string s = "";
  int v = 0;
  int st = (t.size() - 1) / 2;
  for (int i = 0; i < (int)t.size(); i++) {
    int r;
    if (i % 2 == 0) {
      r = -1;
    } else {
      r = 1;
    }
    s += t[r * v + st];
    st = r * v + st;
    v++;
  }
  cout << s;
  return 0;
}
