n,m = gets.split.map(&:to_i)
x = n.times.map{[]}
at = 0
m.times{
  a,b=gets.split.map(&:to_i)
  at=a
  x[a] << b
  x[b] << a
}

uni = 0
odd = 0
x.each{|t|
  s = t.size
  uni += 1 if s>0
  odd += 1 if s%2==1
}

con = 0
q = [at]
ch = Array.new(n, false)#キューに入れたかどうかでチェック
while q.size>0
  now = q.pop
  x[now].each{|ne|
    next if ch[ne]
    q << ne
    ch[ne] = true
  }
  con+=1
end


if con<uni then
  puts 'NO'
  exit
end


if odd==0 || odd==2 then
  puts 'YES'
else
  puts 'NO'
end