// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}


int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(n);
  cin >> a;
  a.resize(201, 0);
  int res = inf;
  for(int i = 1; i <= 100; i++){
    int pos = 0, neg = 0;
    for(int j = 1; j <= i; j++){
      if(j > a[j-1]){
        pos += j - a[j-1];
      }else{
        neg += a[j-1] - j;
      }
      if(j == i)continue;
      if(j > a[2*i-1-j]){
        pos += j - a[2*i-1-j];
      }else{
        neg += a[2*i-1-j] - j;
      }
    }
    int ri = 0;
    for(int j = 2 * i - 1; j < n; j++){
      ri += a[j];
    }
//     if(pos > neg){
//       if(pos - neg <= ri){
//         res = min(res, pos + ri - pos + neg);
//       }
//     }else{
//       res = min(res, ri + neg - pos);
//     }
    //cout << i << " " << pos << " " << neg << " " << ri << endl;
    if(pos <= ri + neg)res = min(res, neg + ri);
  }
  cout << res << endl;
	return 0;
}