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 Ruby (2.3.3) (judge verdict: Wrong Answer)

n = gets.to_i
nums = gets.split.map(&:to_i)
nonzero_index = nums.find_index { |i| i.nonzero? }
if nonzero_index.even? && nums[nonzero_index] > 0
  next_minus = false
elsif nonzero_index.even? && nums[nonzero_index] < 0
  next_minus = true
elsif nonzero_index.odd? && nums[nonzero_index] > 0
  next_minus = true
else
  next_minus = false
end
cumulative = 0
ans = 0
nums.each do |num|
  cumulative += num
  if next_minus
    if cumulative >= 0
      decrement = cumulative.abs + 1
      ans += decrement
      cumulative -= decrement
    end
  else
    if cumulative <= 0
      increment = cumulative.abs + 1
      ans += increment
      cumulative += increment
    end
  end
  next_minus = !next_minus 
end
puts ans