#include <bits/stdc++.h>
using namespace std;
const int maxN = 4e5 + 10;
const int MOD = 998244353;
int main() {
  char s[50];
  scanf("%s", s + 1);
  int n = strlen(s + 1), f;
  if (n & 1)
    f = (n + 1) / 2;
  else
    f = n / 2;
  int l = f - 1, r = f + 1;
  cout << s[f];
  for (int i = 1; i < n; i++) {
    if (r <= n) cout << s[r++];
    if (l >= 1) cout << s[l--];
  }
  puts("");
}
