#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, l = 1, r;
  cin >> n;
  r = n;
  if (n == 1) {
    cout << 1 << endl << 1;
    return 0;
  }
  if (n == 2) {
    cout << 1 << endl << 1;
    return 0;
  }
  if (n == 3) {
    cout << 2 << endl << 1 << ' ' << 3;
    return 0;
  }
  if (n == 4) {
    cout << 4 << endl << 2 << ' ' << 4 << ' ' << 1 << ' ' << 3;
    return 0;
  }
  if (n == 5) {
    cout << 5 << endl << 1 << ' ' << 3 << ' ' << 5 << ' ' << 2 << ' ' << 4;
    return 0;
  }
  vector<long long> a(n + 1);
  long long f = 0;
  for (long long i = 1; i <= n; i++) {
    if (f) {
      a[l] = i;
      l++;
    } else {
      a[r] = i;
      r--;
    }
    f += 1;
    f %= 2;
  }
  for (long long i = 1; i < n; i++) {
    if (abs(a[i] - a[i + 1]) == 1) {
      swap(a[i + 1], a[n]);
    }
  }
  cout << n << "\n";
  ;
  for (long long i = 1; i <= n; i++) {
    cout << a[i] << ' ';
  }
}
