#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000000;
struct slope_trick{
  long long mn;
  priority_queue<long long> L;
  priority_queue<long long, vector<long long>, greater<long long>> R;
  slope_trick(){
    mn = 0;
    L.push(-INF);
    R.push(INF);
  }
  long long get_min(){
    return mn;
  }
  void add_right(long long a){
    mn += max(L.top() - a, (long long) 0);
    L.push(a);
    R.push(L.top());
    L.pop();
  }
  void add_left(long long a){
    mn += max(a - R.top(), (long long) 0);
    R.push(a);
    L.push(R.top());
    R.pop();
  }
};
int main(){
  int N;
  cin >> N;
  vector<long long> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  sort(A.begin(), A.end());
  for (int i = 0; i < N; i++){
    A[i] -= i;
  }
  slope_trick f;
  for (int i = 0; i < N; i++){
    f.add_left(A[i]);
    f.add_right(A[i]);
    while (!f.R.empty()){
      f.R.pop();
    }
    f.R.push(INF);
  }
  cout << f.mn << endl;
}