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