n,m = gets.split.map(&:to_i)

wall = Array.new(m,0)
lines = n.times.map { |i| gets.split.map(&:to_i) }

lines.each do |(l,r)| 
    (l..r).each do |i|
        wall[i] += 1
        wall[m-i-1] += 1
    end
end

puts wall.all? {|v| v <= 2} ? "YES" : "NO"