Problem:
Score : 300 points

Problem Statement

You are given an integer sequence of length N. The i-th term in the sequence is a_i.
In one operation, you can select a term and either increment or decrement it by one.

At least how many operations are necessary to satisfy the following conditions?

For every i (1≤i≤n), the sum of the terms from the 1-st through i-th term is not zero.

For every i (1≤i≤n-1), the sign of the sum of the terms from the 1-st through i-th term, is different from the sign of the sum of the terms from the 1-st through (i+1)-th term.

Constraints

2 ≤ n ≤ 10^5

|a_i| ≤ 10^9

Each a_i is an integer.

Input

Input is given from Standard Input in the following format:

n
a_1 a_2 ... a_n

Output

Print the minimum necessary count of operations.

Sample Input 1

4
1 -3 1 0

Sample Output 1

4

For example, the given sequence can be transformed into 1, -2, 2, -2 by four operations. The sums of the first one, two, three and four terms are 1, -1, 1 and -1, respectively, which satisfy the conditions.

Sample Input 2

5
3 -6 4 -5 7

Sample Output 2

0

The given sequence already satisfies the conditions.

Sample Input 3

6
-1 4 3 2 -5 4

Sample Output 3

8

Solution in PyPy3 (2.4.0) (judge verdict: Wrong Answer)

from sys import stdout
printn = lambda x: stdout.write(str(x))
inn = lambda : int(input())
inl   = lambda: list(map(int, input().split()))
inm   = lambda:      map(int, input().split())
ins = lambda : input().strip()
DBG = True # and False
BIG = 999999999
R = 10**9 + 7

def ddprint(x):
  if DBG:
    print(x)

n = inn()
a = inl()
ne = sum(a[::2])
no = sum(a[1::2])
p0 = (ne>no)
cnt = 0
acc = 0
#ddprint("ne {} no {} p0 {} a {}".format(ne,no,p0,a))
for i in range(n):
    if (p0 if i%2==0 else not p0):
        x = max(0, 1-a[i]-acc)
        cnt += x
        acc += a[i]+x
    else:
        x = max(0, a[i]+acc+1)
        cnt += x
        acc += a[i]-x
    #ddprint("cnt {} acc {}".format(cnt,acc))
print(cnt)