#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <numeric>

using namespace std;

int main() {
	int n;

	cin >> n;
	vector<int> a(n, 0);
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	int total = accumulate(a.begin(), a.end(), 0);
	vector<int> b(n, 0);

	int ans = 1e9;
	for (int len = 1; len <= n; len += 2) {
		vector<int> piramid(len, len / 2 + 1);
		for (int i = 0; i < len / 2; i++) {
			piramid[i] = piramid[len - 1 - i] = i + 1;
		}

		for (int start = 0; start <= n - len; start++) {
			fill(b.begin(), b.end(), 0);
			copy(piramid.begin(), piramid.end(), b.begin() + start);
			int more = 0;
			int less = 0;

			for (int i = 0; i < n; i++) {
				int diff = a[i] - b[i];

				if (diff > 0) {
					more += diff;
				} else {
					less +=  -diff;
				}

			}
			if (more >= less) {
				ans = min(ans, more);
			}
		}
	}
	cout << ans << endl;
	return 0;
}