#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void solve() {
  string s, ans;
  cin >> s;
  int n = (int)s.size();
  ans.resize(n);
  int half = n / 2 - (n % 2 == 0 ? 1 : 0);
  ans[0] = s[half];
  int pos = 0;
  for (int i = half + 1; i < n; ++i) {
    ans[pos * 2 + 1] = s[i];
    pos++;
  }
  pos = 1;
  for (int i = half - 1; i >= 0; --i) {
    ans[pos * 2] = s[i];
    pos++;
  }
  cout << ans;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int t;
  t = 1;
  while (t--) solve();
  return 0;
}
