#include <bits/stdc++.h>
using namespace std;
string S;
stack<char> ans;
int main() {
  cin >> S;
  if (S.length() % 2 == 0) {
    for (int i = 0, j = S.length() - 1; i < j; i++, j--)
      ans.push(S[j]), ans.push(S[i]);
    while (!ans.empty()) {
      cout << ans.top();
      ans.pop();
    }
    cout << "\n";
  } else {
    ans.push(S[0]);
    for (int i = 1, j = S.length() - 1; i < j; i++, j--)
      ans.push(S[j]), ans.push(S[i]);
    while (!ans.empty()) {
      cout << ans.top();
      ans.pop();
    }
    cout << "\n";
  }
  return 0;
}
