#include <iostream>
using namespace std;

const int MAX_N = 110;
int a[MAX_N];

int int_pow(int a, int b) {
    int res = 1;
    for (int i = 0; i < b; i++) res *= a;
    return res;
}

int main() {
    int n, sum = 0;
    cin >> n;

    for (int i = 0; i < n; i++) {
        cin >> a[i];
        sum += a[i];
    }

    int ans = (1 << 28);

    for (int w = 201; w >= 1; w -= 2) {
        int use_block = int_pow((w + 1) / 2, 2);
        if (use_block > sum) continue;

        // すでに置かれているブロックの左端をピラミッドのどこに割り当てるか
        for (int left_end = 0; left_end < w; left_end++) {
            int cost = 0, missing = 0;
            auto between_original = [&](int p) { return left_end <= p && p < left_end + n; };
            for (int b_i = 0; b_i < 400; b_i++) {
                if (b_i >= w) {
                    // 捨て置き場へ
                    if (between_original(b_i)) cost += a[b_i - left_end];
                } else {
                    int height = min(b_i, w - b_i - 1) + 1,
                        cur_height = between_original(b_i) ? a[b_i - left_end] : 0;
                    cost += abs(cur_height - height);
                    if (cur_height < height) missing += height - cur_height;
                }
            }
            ans = min(ans, cost - missing);
        }
    }
    cout << ans << endl;

    return 0;
}