#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int n, i, j, m;
  n = s.size();
  if (n % 2 == 0)
    m = n / 2 - 1;
  else
    m = n / 2;
  cout << s[m];
  i = m + 1;
  j = m - 1;
  for (; i < n; i++, j--) {
    if (i < n) cout << s[i];
    if (j >= 0)
      cout << s[j];
    else
      break;
  }
  return 0;
}
