def lscan; gets.split.map(&:to_i); end

h = {}
h[[2,8]] = 1
h[[3,9]] = 2
h[[7,9]] = 3

cnt = 10

gets.to_i.times do
  a,b,c,d = lscan
  abort h.to_s if h[[c,d]]
  i = h[[a,b]]
  i ||= (cnt += 1)
  h[[a,b]] = nil
  h[[c,d]] = i
end


if h[[5,8]] == 1 && h[[4,8]] == 2 && h[[6,8]] == 3
  puts 'YES'
else
  puts 'NO'
end