#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s;
  cin >> s;
  int len = s.size();
  int s1[100] = {0}, x = 2, y = 1, z = 0, k = 0;
  if (len % 2 == 0) {
    while (x <= len) {
      s1[k] = len - x;
      x += 2;
      k++;
    }
    if (len < x) {
      x = 1;
      while (x <= len - 1) {
        s1[k] = x;
        x += 2;
        k++;
      }
    }
  } else {
    k = 0;
    while (y <= len) {
      s1[k] = len - y;
      y += 2;
      k++;
    }
    if (len < y) {
      y = 1;
      while (y <= len - 1) {
        s1[k] = y;
        y += 2;
        k++;
      }
    }
  }
  char s2[100];
  for (int i = 0; i < len; i++) {
    s2[s1[i]] = s[i];
  }
  for (int i = 0; i < len; i++) cout << s2[i];
}
