R=range
J=lambda:map(int,input().split())
N,M=J()
N+=1
p=[i for i in R(N*2)]
def r(i):
	while i!=p[i]:i=p[i]
	return i
for i in R(M):
	A,B=J()
	C,D=r(A),r(B+N)
	p[C]=D
	C,D=r(A+N),r(B)
	p[C]=D
print("YNeos"[any(r(i)==r(i+N)for i in R(N))::2])