#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, mid;
  char s[51], ans[50];
  cin >> s;
  mid = strlen(s) / 2;
  if (strlen(s) % 2 == 0) mid--;
  j = 0;
  for (i = mid; i >= 0; --i) {
    ans[j] = s[i];
    j += 2;
  }
  if (strlen(s) > 1) j = 1;
  for (i = mid + 1; i < strlen(s); ++i) {
    ans[j] = s[i];
    j += 2;
  }
  for (i = 0; i < strlen(s); ++i) cout << ans[i];
  return 0;
}
