#include <bits/stdc++.h>
using namespace std;
int main() {
  string S;
  cin >> S;
  string res = "";
  int len = S.length();
  if (len % 2 == 0) {
    for (int i = 0; i < len / 2; ++i) {
      res += S[len - 1 - i];
      res += S[i];
    }
  } else {
    for (int i = 0; i < len / 2; ++i) {
      res += S[i];
      res += S[len - 1 - i];
    }
    res += S[len / 2];
  }
  reverse(res.begin(), res.end());
  cout << res;
  return 0;
}
