#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 5;
int main() {
  string s;
  while (cin >> s) {
    int len = s.size();
    if (len % 2 == 0)
      len = len / 2 - 1;
    else
      len = len / 2;
    cout << s[len];
    int k = 1;
    int cot = 0;
    for (int i = 1; i < s.size(); i++) {
      cout << s[len + k];
      k *= -1;
      cot++;
      if (cot % 2 == 0) k++;
    }
    cout << endl;
  }
}
