#if __INCLUDE_LEVEL__ == 0

#include <bits/stdc++.h>

using namespace std;

#undef assert
#define assert(expr) (expr) || (__builtin_unreachable(), 0)

#include __BASE_FILE__

namespace std::ranges::views {

namespace {

struct S {
  priority_queue<int> lower;
  priority_queue<int, vector<int>, ::greater<>> upper;

  explicit S(int x) { lower.push(x); }

  int median() const { return lower.top(); }

  int size() const { return ssize(lower) + ssize(upper); }

  void merge(S s) {
    if (size() < s.size()) {
      swap(*this, s);
    }
    while (ssize(s.lower)) {
      add(s.lower.top());
      s.lower.pop();
    }
    while (ssize(s.upper)) {
      add(s.upper.top());
      s.upper.pop();
    }
  }

  void add(int x) {
    if (::empty(upper) || x < upper.top()) {
      lower.push(x);
    } else {
      upper.push(x);
    }
    while (ssize(upper) < ssize(lower)) {
      upper.push(lower.top());
      lower.pop();
    }
    while (ssize(lower) < ssize(upper)) {
      lower.push(upper.top());
      upper.pop();
    }
  }

  int64_t cost() {
    int m = median();
    int64_t cost = 0;
    while (ssize(lower)) {
      cost += abs(lower.top() - m);
      lower.pop();
    }
    while (ssize(upper)) {
      cost += abs(upper.top() - m);
      upper.pop();
    }
    return cost;
  }
};

void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  cin >> a;
  sort(a);
  for (int i : iota(0, n)) {
    a[i] -= i;
  }
  vector<S> s;
  for (int e : a) {
    S t(e);
    while (ssize(s) && t.median() < s.back().median()) {
      t.merge(::move(s.back()));
      s.pop_back();
    }
    s.push_back(t);
  }
  int64_t ans = 0;
  for (auto&& e : s) {
    ans += e.cost();
  }
  cout << ans << '\n';
}

}  // namespace

}  // namespace std::ranges::views

using views::solve;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  solve();
}

#else  // __INCLUDE_LEVEL__

namespace std {

template <class T1, class T2>
istream& operator>>(istream& is, pair<T1, T2>& p) {
  return is >> p.first >> p.second;
}

template <class... Ts>
istream& operator>>(istream& is, tuple<Ts...>& t) {
  return apply([&is](auto&... xs) -> istream& { return (is >> ... >> xs); }, t);
}

template <class R, enable_if_t<!is_convertible_v<R, string>>* = nullptr>
auto operator>>(istream& is, R&& r) -> decltype(is >> *begin(r)) {
  for (auto&& e : r) {
    is >> e;
  }
  return is;
}

template <class T1, class T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
  return os << p.first << ' ' << p.second;
}

template <class... Ts>
ostream& operator<<(ostream& os, const tuple<Ts...>& t) {
  auto f = [&os](const auto&... xs) -> ostream& {
    [[maybe_unused]] auto sep = "";
    ((os << exchange(sep, " ") << xs), ...);
    return os;
  };
  return apply(f, t);
}

namespace impl {

template <class R>
constexpr int n_dims(char) {
  return 0;
}

template <class R>
constexpr auto n_dims(int) -> decltype(begin(declval<R>()), 0) {
  return n_dims<decltype(*begin(declval<R>()))>(0) + 1;
}

}  // namespace impl

template <class R, enable_if_t<!is_convertible_v<R, string_view>>* = nullptr>
auto operator<<(ostream& os, R&& r) -> decltype(os << *begin(r)) {
  static constexpr int D = impl::n_dims<R>(0);
  static const string SEP = 1 < D ? string(D - 1, '\n') : " ";
  string sep;
  for (auto&& e : r) {
    os << exchange(sep, SEP) << e;
  }
  return os;
}

}  // namespace std

#endif  // __INCLUDE_LEVEL__