#include <bits/stdc++.h>
using namespace std;
int n;
int main() {
  string s;
  cin >> s;
  int n = s.length();
  string s1 = "";
  int i = 0, j = n - 1;
  bool z = false;
  if (n % 2 == 0) z = true;
  while (i <= j) {
    if (z) {
      s1 = s[j] + s1;
      j--;
    } else {
      s1 = s[i] + s1;
      i++;
    }
    z = !z;
  }
  cout << s1;
}
