n=gets.to_i
@g=Hash.new{|h, k| h[k]={}}
n.times do
  x, y, _x, _y=gets.split.map(&:to_i)
  @g[[x, y]][[_x, _y]]=1
  @g[[_x, _y]][[x, y]]=1
end

@used={}

def rec(i, g)
  @used[i]=1
  g<< i
  @g[i].each_key do |j|
    unless @used.key?(j)
      rec(j, g)
    end
  end
end

ok=true
@g.each_key do |i|
  unless @used.key?(i)
    g=[]
    rec(i, g)
    e=g.inject(0){|s, v| s+@g[v].size()}
    ok&=(g.size+1>e/2)
  end
end

puts ok ? "YES": "NO"