n,*a=$<.map{|e|e.split.map(&:to_i).sort}
a.sort!{|x,y|x[0]<=>y[0]}
now=[]
n[0].times do |i|
  g=a[i]+[0]
  r=[]
  now.length.times do |j|
    gg=now[j]
    if gg[0]<g[0] && gg[1]<g[1] && gg[2]<g[2]
      g[3]=gg[3]+1 if g[3]<gg[3]+1
      r<< j
    end
  end
  r.length.times do |j|
    now.delete_at(r[j]-j)
  end
  now<< g
end
c=0
now.each do |e|
  c=e[3] if c<e[3]
end
p c+1