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 Lua (5.3.2) (judge verdict: Wrong Answer)

N = io.read "l"
sum = 0
op = 0
for a in io.read "l":gmatch "%-?%d+" do
    a = tonumber(a)
    if sum > 0 then
        if a >= -sum then
            aNew = -sum - 1
            op = op + math.abs(a - aNew)
            a = aNew
        end
    elseif sum < 0 then
        if a <= -sum then
            aNew = -sum + 1
            op = op + math.abs(a - aNew)
            a = aNew
        end
    end
    sum = sum + a
end
print(op)