#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int x, y;
  cin >> s;
  if ((int)s.size() % 2 == 0) {
    x = (int)s.size() / 2 - 1;
    y = x + 1;
    while (x >= 0 && y <= s.size()) {
      cout << s[x] << s[y];
      x--;
      y++;
    }
    cout << '\n';
    return 0;
  }
  x = (int)s.size() / 2;
  y = x + 1;
  cout << s[x];
  x--;
  while (x >= 0 && y <= (int)s.size()) {
    cout << s[y] << s[x];
    x--;
    y++;
  }
  cout << '\n';
  return 0;
}
