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

template<class T> struct median_priority_queue {
    std::priority_queue<T> pqL;
    std::priority_queue<T, std::vector<T>, std::greater<T>> pqR; 
    median_priority_queue() {
        //pqL.emplace(std::numeric_limits<T>::min());
        //pqR.emplace(std::numeric_limits<T>::max());
    }
    void push(T v){
        if(!pqL.empty() && v < pqL.top()) pqL.emplace(v);
        else pqR.emplace(v);
        update();
    }
    T get(){
        return pqR.top();
    }
    int size(){
        return int(pqL.size() + pqR.size());
    }
    void update(){
        while(pqL.size() + 2 <= pqR.size()){
            pqL.emplace(pqR.top());
            pqR.pop();
        }
        while(pqL.size() > pqR.size()){
            pqR.emplace(pqL.top());
            pqL.pop();
        }
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<int> a(n), b(n), parent(n);
    vector<median_priority_queue<int>> pq(n);
    for(auto &&v : a) cin >> v;
    sort(a.begin(), a.end());
    iota(parent.begin(), parent.end(), 0);
    function<int(int)> leader = [&](int v){
        return v == parent[v] ? v : parent[v] = leader(parent[v]);
    };
    auto merge = [&](int i, int j){
        if(pq[i].size() < pq[j].size()){
            swap(pq[i], pq[j]);
            swap(i, j);
        }
        parent[j] = i;
        auto &tmp = pq[j].pqR;
        while(!tmp.empty()){
            pq[i].push(tmp.top());
            tmp.pop();
        }
        auto &tmp2 = pq[j].pqL;
        while(!tmp2.empty()){
            pq[i].push(tmp2.top());
            tmp2.pop();
        }
    };
    for(int i = 0; i < n; i++){
        b[i] = a[i] - i;
        pq[i].push(b[i]);
    }
    for(int j = 0; j < 60; j++){
    	for(int i = 0; i + 1 < n; i++){
    		int u = leader(i), v = leader(i + 1);
    		if(u == v) continue;
    		if(pq[u].get() >= pq[v].get()) merge(u, v);
    	}
    	for(int i = n - 2; i >= 0; i--){
    		int u = leader(i), v = leader(i + 1);
    		if(u == v) continue;
    		if(pq[u].get() >= pq[v].get()) merge(u, v);
    	}
    }
    ll ans = 0;
    for(int i = 0; i < n; i++){
        ans += abs(b[i] - pq[parent[leader(i)]].get());
    }
    cout << ans << '\n';
}