INF = 1<<32
M = 200
N = int(input())
A = list(map(int,input().split()))
ans = INF
for Len in range(1,M,2):
    P = [0] * M
    cnt = 1
    Mid = Len // 2
    for i in range(Len):
        P[i] = cnt
        if i < Mid:
            cnt += 1
        else:
            cnt -= 1
    Q = [0] * M
    for i in range(N):
        Q[i] = A[i]
    ret = 0
    cnt = 0
    for i in range(M):
        if P[i] < Q[i]:
            ret += Q[i] - P[i]
            cnt += Q[i] - P[i]
        else:
            cnt -= P[i] - Q[i]
    if cnt < 0:
        ret += INF
    ans = min(ans, ret)
print(ans)