#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
long long int power(long long int x, long long int y, long long int p) {
  long long int res = 1;
  x = x % p;
  if (x == 0) return 0;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;
  while (t--) {
    long long int n, k, q, i, j, a, b, x, y, m, count = 0, sum = 0, pro = 1,
                                                count1 = 0, flag = 0;
    string s;
    cin >> s;
    n = s.length();
    j = (n - 1) / 2;
    i = j - 1;
    cout << s[j];
    j++;
    while (i >= 0 || j < n) {
      cout << s[j];
      j++;
      if (i >= 0) {
        cout << s[i];
        i--;
      }
    }
  }
}
