#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

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

end_i = Sa

for i in range(N):
	num = array[i].count(True)
	if num%2 == 1:
		end += 1
		end_i = i
		if end >= 3:
			print("NO")
			exit(0)

def search (i,j):
	global array
	global count
	count += 1	

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

	for k in range(N):
		if array[j][k] == True:
			search(j,k)

for i in range(N):
	if (array[end_i][i] == True):
		search(end_i,i)
		break

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