#include <bits/stdc++.h>
int main() {
  char str[50], str2[50];
  int i, j, l, k = 0, n, m, s;
  gets(str);
  l = strlen(str);
  if (l == 1)
    printf("%s", str);
  else {
    str2[l] = '\0';
    if (l % 2 == 0) {
      s = l - 1;
      n = l / 2;
      m = l / 2;
      for (i = 0, j = l - 1; i < m;) {
        if (k == 0) {
          str2[s] = str[j];
          k = 1;
          j--;
          s--;
        } else if (k == 1) {
          str2[s] = str[i];
          k = 0;
          i++;
          s--;
        }
        if (s < 0) break;
      }
    } else {
      s = l - 1;
      n = (l / 2);
      for (i = 0, j = l - 1; i <= n;) {
        if (k == 1) {
          str2[s] = str[j];
          k = 0;
          j--;
          s--;
        } else if (k == 0) {
          str2[s] = str[i];
          k = 1;
          i++;
          s--;
        }
        if (s < 0) break;
      }
    }
    printf("%s", str2);
  }
  return 0;
}
