#include <bits/stdc++.h>
using namespace std;
string a, b;
int k;
int main() {
  cin >> a;
  k = 1;
  if (a.size() % 2 == 0) {
    while (k != a.size() + 1) {
      if (k % 2 != 0) {
        b += a[a.size() - k / 2 - 1];
      } else {
        b += a[k / 2 - 1];
      }
      k++;
    }
  } else {
    while (k != a.size() + 1) {
      if (k % 2 == 0) {
        b += a[a.size() - k / 2];
      } else {
        b += a[k / 2];
      }
      k++;
    }
  }
  reverse(b.begin(), b.end());
  cout << b;
}
