N, M = gets.split.map(&:to_i)
E = Hash.new { |h, k| h[k] = [] }

M.times do
  a, b = gets.split.map(&:to_i)
  E[a] << b
  E[b] << a
end

def is_connected_graph?
  queue = []
  queue << E.first.first
  visited = Array.new(N + 1, false)
  cnt = 0

  until queue.empty?
    v = queue.shift

    next if visited[v]
    visited[v] = true
    cnt += 1

    E[v].each do |u|
      queue << u
    end
  end

  cnt == E.size
end

def f
  E.all? { |u, list| list.size.even? }
end

def g
  odd_cnt = 0
  even_cnt = 0

  E.each do |u, list|
    if list.size.even?
      even_cnt += 1
    else
      odd_cnt += 1
    end
  end

  odd_cnt == 2
end

if is_connected_graph? && (f || g)
  puts 'YES'
else
  puts 'NO'
end