class UnionFind
  def initialize(n); @data = Array.new(n, &:itself); end
  def root(i); _compact(i, _root(i)); end
  def unite!(i,j); _compact(i, root(j)); end
  def same?(i,j); root(i) == root(j); end
    
  def _root(i); i = @data[i] until @data[i] == i; return i; end
  def _compact(i, r); @data[i], i = r, @data[i] until @data[i] == r; return r; end
end

N, M = gets.split.map(&:to_i)
D = Array.new(N, 0)
R = UnionFind.new(N)
M.times do
  a, b = gets.split.map(&:to_i)
  D[a] += 1
  D[b] += 1
  R.unite!(a,b)
end

s = D.index{|v| v > 0 }
o = N.times.count{|i| D[i].odd? }
if o == 2 || o == 0
  puts D.each_with_index.all?{|c,u| c.zero? ^ R.same?(s, u) } ? "YES" : "NO"
else
  puts "NO"
end