#include <bits/stdc++.h>

#define show(x) cout << #x << " = " << x << endl

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz=" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = 1e9 + 7;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 100;

int main()
{
    int N;
    cin >> N;
    vector<int> A(N, 0);
    int sum = 0;
    for (ll i = 0; i < N; i++) {
        cin >> A[i];
        sum += A[i];
    }
    const int maxi = (int)sqrt(sum);
    int mini = 1000000;
    for (int m = 1; m <= maxi; m++) {
        const int maximum = 2 * maxi - 2;
        int plus = 0;
        int minus = 0;
        for (int i = 0; i < N; i++) {
            const int num = (i > maximum) ? 0 : (i < maxi) ? i + 1 : maximum - i + 1;
            if (A[i] > num) {
                plus += A[i] - num;
            } else if (A[i] < num) {
                minus += num - A[i];
            }
        }
        mini = min(mini, max(plus, minus));
    }
    cout << mini << endl;

    return 0;
}