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