#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define per(i, n) for (int i = (n)-1; i >= 0; i--)
#define rep2(i, l, r) for (int i = (l); i < (r); i++)
#define per2(i, l, r) for (int i = (r)-1; i >= (l); i--)
#define each(e, v) for (auto &e : v)
#define MM << " " <<
#define pb push_back
#define eb emplace_back
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

template <typename T>
using minheap = priority_queue<T, vector<T>, greater<T>>;

template <typename T>
using maxheap = priority_queue<T>;

template <typename T>
bool chmax(T &x, const T &y) {
    return (x < y) ? (x = y, true) : false;
}

template <typename T>
bool chmin(T &x, const T &y) {
    return (x > y) ? (x = y, true) : false;
}

template <typename T>
int flg(T x, int i) {
    return (x >> i) & 1;
}

int popcount(int x) { return __builtin_popcount(x); }
int popcount(ll x) { return __builtin_popcountll(x); }
int topbit(int x) { return (x == 0 ? -1 : 31 - __builtin_clz(x)); }
int topbit(ll x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); }
int botbit(int x) { return (x == 0 ? -1 : __builtin_ctz(x)); }
int botbit(ll x) { return (x == 0 ? -1 : __builtin_ctzll(x)); }

template <typename T>
void print(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' ');
    if (v.empty()) cout << '\n';
}

template <typename T>
void printn(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << '\n';
}

template <typename T>
int lb(const vector<T> &v, T x) {
    return lower_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
int ub(const vector<T> &v, T x) {
    return upper_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
void rearrange(vector<T> &v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <typename T>
vector<int> id_sort(const vector<T> &v, bool greater = false) {
    int n = v.size();
    vector<int> ret(n);
    iota(begin(ret), end(ret), 0);
    sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; });
    return ret;
}

template <typename T>
void reorder(vector<T> &a, const vector<int> &ord) {
    int n = a.size();
    vector<T> b(n);
    for (int i = 0; i < n; i++) b[i] = a[ord[i]];
    swap(a, b);
}

template <typename T>
T floor(T x, T y) {
    assert(y != 0);
    if (y < 0) x = -x, y = -y;
    return (x >= 0 ? x / y : (x - y + 1) / y);
}

template <typename T>
T ceil(T x, T y) {
    assert(y != 0);
    if (y < 0) x = -x, y = -y;
    return (x >= 0 ? (x + y - 1) / y : x / y);
}

template <typename S, typename T>
pair<S, T> operator+(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first + q.first, p.second + q.second);
}

template <typename S, typename T>
pair<S, T> operator-(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first - q.first, p.second - q.second);
}

template <typename S, typename T>
istream &operator>>(istream &is, pair<S, T> &p) {
    S a;
    T b;
    is >> a >> b;
    p = make_pair(a, b);
    return is;
}

template <typename S, typename T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
    return os << p.first << ' ' << p.second;
}

struct io_setup {
    io_setup() {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

const int inf = (1 << 30) - 1;
const ll INF = (1LL << 60) - 1;
// const int MOD = 1000000007;
const int MOD = 998244353;

template <typename T>
struct Slope_Trick {
    priority_queue<T> l;
    priority_queue<T, vector<T>, greater<T>> r;
    const T INF_T = numeric_limits<T>::max() / 2;
    T add_l, add_r;
    T min_f = 0;

    // f(x) = 0 で初期化
    Slope_Trick() : add_l(0), add_r(0) {
        l.push(-INF_T);
        r.push(INF_T);
    }

    T get_min() const { return min_f; };

    void add_constant(const T &c) { min_f += c; };

    // f(x) += max(-x+a, 0)
    void add_line_left(const T &a) {
        if (a > r.top() + add_r) {
            min_f += -(r.top() + add_r) + a;
            l.push(r.top() + add_r - add_l);
            r.pop();
            r.push(a - add_r);
        } else {
            l.push(a - add_l);
        }
    }

    // f(x) += max(x-a, 0)
    void add_line_right(const T &a) {
        if (a < l.top() + add_l) {
            min_f += (l.top() + add_l) - a;
            r.push(l.top() + add_l - add_r);
            l.pop();
            l.push(a - add_l);
        } else {
            r.push(a - add_r);
        }
    }

    // f(x) += |x-a|
    void add_abs(const T &a) {
        add_line_left(a);
        add_line_right(a);
    }

    // f(x) <- min{f(y) | y <= x}
    void left_min() {
        while ((int)r.size() > 1) r.pop();
    }

    // f(x) <- min{f(y) | y >= x}
    void right_min() {
        while ((int)l.size() > 1) l.pop();
    }

    // f(x) <- min{f(y) | x-b <= y <= x-a}
    void slide_min(const T &a, const T &b) {
        assert(a <= b);
        add_l += a;
        add_r += b;
    }

    // f(x) <- f(x-a)
    void shift(const T &a) {
        add_l += a;
        add_r += a;
    }

    // f(x) を入手 (ただし、l と r は破壊される)
    T get(const T &x) {
        T ret = min_f;
        while (!l.empty()) {
            ret += max(T(0), -x + (l.top() + add_l));
            l.pop();
        }
        while (!r.empty()) {
            ret += max(T(0), x - (r.top() + add_r));
            r.pop();
        }
        return ret;
    }
};

void solve() {
    int N;
    cin >> N;

    vector<int> a(N);
    rep(i, N) cin >> a[i];

    sort(all(a));
    rep(i, N) a[i] -= i;

    Slope_Trick<ll> st;

    rep(i, N) {
        st.left_min();
        st.add_abs(a[i]);
    }

    cout << st.get_min() << '\n';
}

int main() {
    int T = 1;
    // cin >> T;
    while (T--) solve();
}