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