N,M = map(int,raw_input().split())
E = [[] for i in xrange(N)]
for i in xrange(M):
	A,B = map(lambda x:int(x)-1,raw_input().split())
	E[A].append(B)
	E[B].append(A)
for i in xrange(N):
	E[i].sort()
def check(gone,nxt):
	while gone:
		if gone % 10000 == nxt:
			return True
		gone /= 10000
	return False
def dfs(h,gone,num):
	if num == 5:
		if E[h][0] == 0:
			print "YES"
			quit()
	else:
		for nxt in E[h]:
			if check(gone,nxt):
				continue
			dfs(nxt,gone*10000+nxt,num+1)
dfs(0,0,1)
print "NO"