#include <bits/stdc++.h>
using namespace std;
int n, p[100];
int main() {
  cin >> n;
  for (int i = 1; i <= n / 2; ++i) cin >> p[i];
  int odd = 0;
  for (int i = 1, at = 1; i <= n / 2; ++i, at += 2) {
    odd += abs(at - p[i]);
  }
  int even = 0;
  for (int i = n / 2, at = n; i >= 1; --i, at -= 2) {
    even += abs(at - p[i]);
  }
  printf("%d\n", min(odd, even));
}
