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 Python (3.8.2) (judge verdict: Accepted)

n=int(input())
a=list(map(int,input().split()))
ans_o=0
cnt_o=0
ans_e=0
cnt_e=0
for i in range(n):
  cnt_o+=a[i]
  if i%2==0:
    if cnt_o>0:
      continue
    else:
      ans_o+=abs(cnt_o)+1
      cnt_o=1
  else:
    if cnt_o<0:
      continue
    else:
      ans_o+=cnt_o+1
      cnt_o=-1
for i in range(n):
  cnt_e+=a[i]
  if i%2==0:
    if cnt_e<0:
      continue
    else:
      ans_e+=cnt_e+1
      cnt_e=-1
  else:
    if cnt_e>0:
      continue
    else:
      ans_e+=abs(cnt_e)+1
      cnt_e=1
print(min(ans_o,ans_e))