#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int len = s.length();
  int x = 0;
  if (len % 2 == 0)
    x = len / 2 - 1;
  else
    x = len / 2;
  cout << s[x];
  int j = 1;
  while (j <= len / 2) {
    if (x + j <= len) cout << s[x + j];
    if (x - j >= 0) cout << s[x - j];
    j++;
  }
  return 0;
}
