N = int(input())
A = [int(i) for i in input().split()]
a,b = 1,3
while a+b<= sum(A):
	a+=b
	b+=2
L = b - 2
B = [0 for i in range(L)]
for i in range(L):
	if i < L // 2:
		B[i] = (i + 1)
	elif i > L // 2:
		B[i] = L - i
	else:
		B[i] = L // 2 + 1
m =  10 ** 9 + 7
while len(A) < L:
	A.append(0)
N = len(A)
for i in range(N - L + 1):
	plus,minus = 0,0
	for j in range(L):
		if A[i + j] >= B[j]:
			minus += A[i + j] - B[j]
		else:
			plus += B[j] - A[i + j]
	m = min(m,sum(A) - sum(B) + plus)
print(m)