#include <bits/stdc++.h>
int main() {
  char s[50], s1[50];
  scanf("%s", s);
  int i, l, h, c = 0;
  l = strlen(s);
  if (l % 2 == 0)
    h = l / 2 - 1;
  else
    h = l / 2;
  for (i = 0; i < l; i++) {
    s1[i] = s[h];
    c++;
    if (i % 2 == 0)
      h = h + c;
    else
      h = h - c;
  }
  s1[l] = '\0';
  printf("%s", s1);
  return 0;
}
