N, M = map(int, input().split())
edges = []
g = [set() for _ in range(N)]
for _ in range(M):
	A, B = map(int, input().split())
	A -= 1
	B -= 1
	g[A].add(B)
	g[B].add(A)
	edges.append((A, B))
e2 = []
for a, b in edges:
	if a == 0 or b == 0:
		continue
	if a in g[0]:
		e2.append((a, b))
	if b in g[0]:
		e2.append((b, a))
for i, j in e2:
	for k, l in e2:
		if i != k and l in g[j]:
			print("YES")
			exit()
print("NO")