output_description: Print the minimum necessary count of operations.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      n
      a_1 a_2 ... a_n
attempt: n = int(input())
  sa = input().split()
  
  a = [0 for i in range(n)]
  sumeven = 0
  sumodd = 0
  for i,sai in enumerate(sa):
      a[i] = int(sai)
  
      if i % 2 == 0:
          sumeven += a[i]
      else:
          sumodd += a[i]
  
  ret = 0
  sm = 0
  for i,ai in enumerate(a):
      if i % 2 == 1:
              ret += max(-sm+1-ai,0)
              sm += max(ai, -sm+1)
          else:
              ret += max(sm+1 + ai, 0)
              sm += min(ai, -(sm+1))
  ret2 = 0
  sm = 0
  for i,ai in enumerate(a):
      if i % 2 == 0:
          ret2 += max(-sm+1-ai,0)
          sm += max(ai, -sm+1)
      else:
          ret2 += max(sm+1 + ai, 0)
          sm += min(ai, -(sm+1))
          
  print(max(ret,ret2))
      
problem_description: 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.
samples: [{"input": "4\n    1 -3 1 0", "output": "4\n    \n\nFor example, the given sequence can be transformed into 1, -2, 2, -2 by four\noperations. The sums of the first one, two, three and four terms are 1, -1, 1\nand -1, respectively, which satisfy the conditions.\n\n* * *"}, {"input": "5\n    3 -6 4 -5 7", "output": "0\n    \n\nThe given sequence already satisfies the conditions.\n\n* * *"}, {"input": "6\n    -1 4 3 2 -5 4", "output": "8"}]