#input of int(split by space)
def get_i()
  return gets.chomp.split(" ").map(&:to_i)
end
#input of float(split by space)
def get_f()
  return gets.chomp.split(" ").map(&:to_f)
end
#input of string(split by space)
def get()
  return gets.chomp.split(" ")
end
#input of string(split per one character)
def get_nsp()
  return gets.chomp.split("")
end
#yes or no decision
def yn_judge(bool,y="Yes",n="No")
  return bool ? y : n 
end
#create of array
def array(size1,init=nil,size2=-1)
  if size2==-1
      return Array.new(size1){init}
  else
      return Array.new(size2){Array.new(size1){init}}
  end
end

def max(a,b)
    return a>b ? a : b
end

def min(a,b)
    return a>b ? b : a
end

INF=Float::INFINITY

N=gets.to_i
xy=array(N)
N.times do|i|
    xy[i]=get_i
end
xy.sort!{|a,b| (a[0]**2+a[1]**2)**0.5<=>(b[0]**2+b[1]**2)**0.5}
ans=0
nx,ny=xy[0]
pq=Hash.new(Hash.new(0))
(N-1).times do|i|
  x,y=xy[i+1]
  dx,dy=nx-x,ny-y
  if pq[dy][dx].zero?
      ans+=1
      pq[dy][dx]=1
  end
  nx,ny=x,y
end
puts ans