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 = x.select{|t| t.size>0}.size

con = 0
q = [at]
ch = Array.new(n, false)
while q.size>0
  now = q.shift
  ch[now] = true
  x[now].each{|ne|
    next if ch[now]
    q<<ne
  }
  con+=1
end

if con<uni then
  puts 'NO'
  exit
end

odd = x.select{|t| t.size%2==1}.size

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