#include <bits/stdc++.h>
using namespace std;
int main() {
  int i = 0;
  string a;
  cin >> a;
  stack<char> q;
  int len = a.length();
  if (len % 2 == 0) {
    while (i < len / 2) {
      q.push(a[len - i - 1]);
      q.push(a[i]);
      i++;
    }
  } else {
    while (i < len / 2) {
      q.push(a[i]);
      q.push(a[len - i - 1]);
      i++;
    }
    q.push(a[len / 2]);
  }
  while (!q.empty()) {
    cout << q.top();
    q.pop();
  }
  return 0;
}
