while n = gets.to_i
  break if n == 0
  arr = []
  n.times{|i|
    arr << gets.split(",").map(&:to_f)
  }
  arr.sort!
  max = []
  min = []
  n.times{|i|
    (i+1).upto(n-1){|j|
      del = (arr[j][1] - arr[i][1]) / (arr[j][0] - arr[i][0])
      max[i] ||= [del, j]
      min[i] ||= [del, j]
      max[i] = [del, j] if max[i][0] < del
      min[i] = [del, j] if min[i][0] > del
    }
  }
  used = [0]
  i = 0
  loop do
    i = max[i][1]
    used << i
    break if i == n - 1
  end
  i = 0
  loop do
    i = min[i][1]
    break if i == n - 1
    used << i
  end
  p n - used.size
end