// yukicoder: 77 レンガのピラミッド
// 2019.6.1 bal4u

#include <stdio.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in()    // 非負整数の入力
{
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

int A[202], N;

int calc(int k) {
	int i, j, a, b;
	
	a = b = 0, j = 1;
	for (i = 1; i <= k; i++) {
		if (A[j] > i) a += A[j]-i;
		else if (A[j] < i) b += i-A[j];
		j++;
	}
	for (i = k-1; i > 0; i--) {
		if (A[j] > i) a += A[j]-i;
		else if (A[j] < i) b += i-A[j];
		j++;
	}
	while (j <= N) a += A[j++];
	if (a < b) a = b;
	return a;
}

int main()
{
	int i, k, s, ans;
	
	N = in();
	s = 0; for (i = 1; i <= N; i++) A[i] = in(), s += A[i];
	for (k = 1; k*k < s; k++);
	if (k*k > s) k--;
	ans = calc(k);
	printf("%d\n", ans);
	return 0;
}