#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  string s;
  char t[50];
  cin >> s;
  int n = (int)s.length();
  int n_res = n, pos = 1;
  n--;
  n /= 2;
  t[0] = s[n];
  for (int i = n + 1; i < n_res; i++) {
    t[pos] = s[i];
    pos += 2;
  }
  pos = 2;
  for (int i = n - 1; i >= 0; i--) {
    t[pos] = s[i];
    pos += 2;
  }
  for (int i = 0; i < n_res; i++) cout << t[i];
  cout << endl;
  return 0;
}
