#include <bits/stdc++.h>
using namespace std;
int main() {
  string a;
  cin >> a;
  string answer;
  int l, r;
  if (a.size() % 2) {
    answer += a[a.size() / 2];
    l = a.size() / 2, r = a.size() / 2;
  } else {
    answer += a[a.size() / 2 - 1];
    l = a.size() / 2 - 1, r = a.size() / 2 - 1;
  }
  int n = 1;
  if (a.size() == 1) {
    cout << a;
    return 0;
  }
  while (l != 0 || r != a.size() - 1) {
    if (n == 1) {
      r += 1;
      answer += a[r];
      n = 0;
    } else if (n == 0) {
      l -= 1;
      answer += a[l];
      n = 1;
    }
  }
  cout << answer;
}
