N, M = gets.split.map &:to_i
edges = []
$<.map{|s|
  a, b = s.split.map &:to_i
  edges << [a, b]
}

used = [false]*M
f=->e{
  return if used[e]
  used[e] = true
  edges[e].each{|a|
    M.times{|i|
      next if edges[i][0]!=a&&edges[i][1]!=a || used[i]
      f[i]
    }
  }
}
f[0]
p used
h=[0]*N
edges.each{|a,b|
  h[a]^=1
  h[b]^=1
}
puts used.all? && h.sum<3 ? :YES : :NO