#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int n = s.size();
  int t = (n - 1) / 2;
  for (int i = 0; i < n; i++) {
    if (i & 1)
      cout << s[t += i];
    else
      cout << s[t -= i];
  }
  return 0;
}
