#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t = 1;
  while (t--) {
    string s;
    cin >> s;
    int n = s.size(), mid = (n + n % 2) / 2 - 1, midLeft = (n + n % 2) / 2 - 2;
    string ans;
    ans += s[mid];
    mid++;
    for (long long i = 0; i < n - 1; i++) {
      if (i % 2 == 0) {
        ans += s[mid];
        mid++;
      } else {
        ans += s[midLeft];
        midLeft--;
      }
    }
    cout << ans;
  }
  return 0;
}
