#include <bits/stdc++.h>
using ull = unsigned long long;
using ll = long long;
using ld = long double;
using namespace std;
const ll mod = 1e9 + 7;
const int N = 3e5 + 5;
void test_case() {
  string s;
  cin >> s;
  int n = ((int)(s).size());
  if (n % 2) {
    int i = n / 2;
    cout << s[i];
    n--;
    int l = i - 1, r = i + 1;
    while (n) {
      cout << s[r] << s[l];
      r++;
      l--;
      n -= 2;
    }
  } else {
    int l = n / 2 - 1, r = n / 2;
    while (n) {
      cout << s[l] << s[r];
      r++;
      l--;
      n -= 2;
    }
  }
}
int main() {
  test_case();
  return 0;
}
