output_description: If the product is positive, print `Positive`. If it is negative, print
  `Negative`. If it is zero, print `Zero`.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      a b
attempt: redBalls = []
  currentRedBall = 0
  
  
  def putBall(i, balles, routes):
      global redBalles
      global currentRedBall
      if i == len(routes):
          redBalles[currentRedBall] = 1
          return None
      _from = routes[i][0] - 1
      _to = routes[i][1] - 1
      if balles[_from] % 2 == 0:
          balles[_from] -= 2
          balles[_to] += 2
          putBall(i + 1, balles, routes)
      else:
          if balles[_from] == 1:
              balles[_from] -= 1
              balles[_to] += 1
              currentRedBall = _to
              putBall(i + 1, balles, routes)
          else:
              _balles = [b for b in balles]
              _balles[_from] -= 1
              _balles[_to] += 1
              currentRedBall = _to
              putBall(i + 1, _balles, routes)
  
              _balles = [b for b in balles]
              _balles[_from] -= 2
              _balles[_to] += 2
              currentRedBall = _from
              putBall(i + 1, _balles, routes)
  
  
  def answer(n, routes):
      global redBalles
      redBalles = [0] * n
      balles = [1] + [2] * (n - 1)
      putBall(0, balles, routes)
      return sum(redBalles)
  
  
  n, m = map(int, input().split())
  routes = []
  for _ in range(m):
      routes.append(list(map(int, input().split())))
  print(answer(n, routes))
  
problem_description: Statement
  
  You are given two integers a and b (a≤b). Determine if the product of the
  integers a, a+1, …, b is positive, negative or zero.
samples: [{"input": "1 3", "output": "Positive\n    \n\n1\u00d72\u00d73=6 is positive.\n\n* * *"}, {"input": "-3 -1", "output": "Negative\n    \n\n(-3)\u00d7(-2)\u00d7(-1)=-6 is negative.\n\n* * *"}, {"input": "-1 1", "output": "Zero\n    \n\n(-1)\u00d70\u00d71=0."}]