#C問題:鉄道同好会


N,M = map(int,input().split(" "))


array = [[False]*N for i in range(N)]
end = 0
count = 0
end_i = []
val = []

def search (i,j):
	global array
	global count
	global end_i

	count += 1	

	array[i][j] = False
	array[j][i] = False

	for k in range(N):
		if array[j][k]:
			tmp = search(j,k)
			if end_i[1] == tmp or i == tmp:
				return end_i[1]
			else:
				return tmp

		elif k == N-1:
			return j

for i in range(M):
	Sa,Sb = map(int,input().split(" "))
	array[Sa][Sb] = True
	array[Sb][Sa] = True



#オイラーグラフか半オイラーグラフかの判定
for i in range(N):
	num = array[i].count(True)
	if num%2 == 1:
		end += 1
		end_i.append(i)
		if end >= 3:
			print("NO")
			exit(0)

if end == 0:
	end_i.append(Sa)
	end_i.append(Sa)


for i in range(N):
	if array[end_i[0]][i]:
		val.append(end_i[1]==search(end_i[0],i))


if all(val) and count == M:
	print("YES")
else:
	print("NO")