n,m = gets.split.map(&:to_i)
wall = Array.new(m,0)
puts n.times.all? { 
    l,r = gets.split.map(&:to_i)
    
    (l..r).inject(0) { |max, i|
        wall[i] += 1
        wall[m - i - 1] += 1
        [max, wall[i], wall[m-i-1]].max
    } < 3
    
} ? "YES" : "NO"