#include <bits/stdc++.h>
using namespace std;

#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
using namespace __gnu_pbds; 

typedef long long int ll;
typedef long int li;

const ll mod = 1000000007;
const ll inf = 1000000000000000000;

typedef vector<int> vi;
typedef vector<li> vli;
typedef vector<ll> vll;
typedef vector<string> vs;
typedef vector<vi> vvi;
typedef vector<vli> vvli;
typedef vector<vll> vvll;
typedef vector<vs> vvs;
typedef map<ll, ll> mll;
typedef map<ll, string> mls;
typedef map<string, ll> msl;
typedef pair<ll, ll> pll;

#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> 
#pragma GCC optimize ("-O3")
#define FAST ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); 
#define PI 3.14159265358979323846
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define pq priority_queue
#define lb lower_bound
#define ub upper_bound
#define tol(s) transform(s.begin(), s.end(), s.begin(), ::tolower);
#define tou(s) transform(s.begin(), s.end(), s.begin(), ::toupper);
#define all(v) v.begin(), v.end()
#define FOR(i, j, k, in) for(li i=j; i<k; i+=in)
#define RFOR(i, j, k, de) for(li i=j; i>=k; i-=de)
#define rep(i,j,k) FOR(i, j, k, 1)
#define rrep(i,j,k) RFOR(i, j, k, 1)
#define repc(v) for(auto it=v.begin(); it!=v.end(); it++)
#define T ll t; cin>>t; while(t--)

ll gen(){
    ll temp;
    cin>>temp;
    return temp;
}

int main(){
  FAST

  ll n;
  cin>>n;
  vll v(n/2);
  generate(all(v),gen);
  
  ll o=0,e=0,a=1;
  rep(i,0,n/2){
      o+=abs(v[i]-a);
      a+=2;
  }
  
  a=2;
  rep(i,0,n/2){
      e+=abs(v[i]-a);
      a+=2;
  }
  
  cout<<min(o,e)<<"\n";
  
  return 0;
}





