#include <bits/stdc++.h>
using namespace std;
int main() {
  string str, ans;
  cin >> str;
  if (str.length() == 1 || str.length() == 2) {
    ans = str;
  } else if (str.length() % 2 == 0) {
    int indc = str.length() / 2 - 1;
    ans += str[indc];
    for (int i = 1; i <= str.length() / 2 - 1; i++) {
      ans += str[indc + i];
      ans += str[indc - i];
    }
    ans += str[str.length() - 1];
  } else {
    int indc = str.length() / 2;
    ans += str[indc];
    for (int i = 1; i <= str.length() / 2; i++) {
      ans += str[indc + i];
      ans += str[indc - i];
    }
  }
  cout << ans;
}
