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)

#!/usr/bin/env ruby
#

n = STDIN.gets.to_i
a = STDIN.gets.split(' ').map{|x| x.to_i}
s = Array.new(n,0)
output = 0

s[0] = a[0]
1.upto(n-1) do |i|
	s[i] = s[i-1] + a[i]
	if s[i] == 0
		change = 1
		s[i] = (s[i-1] > 0) ? -1 : 1
	else
		if (s[i-1] > 0) ^ (s[i] > 0)
			change = 0
		else
			change = s[i].abs+1
			s[i] = (s[i-1] > 0) ? -1: 1
		end
	end
	output += change
end
puts output