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