#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, l, r, c;
  string s, ans;
  cin >> s;
  n = s.size();
  l = 0;
  r = s.size() - 1;
  if (n % 2 == 0)
    c = 0;
  else
    c = 1;
  while (r >= l) {
    if (c == 0) {
      ans = ans + s[r];
      r--;
    } else {
      ans = ans + s[l];
      l++;
    }
    c = 1 - c;
  }
  reverse(ans.begin(), ans.end());
  cout << ans;
  return 0;
}
