import sre_constants
import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (1, 0), (0, -1), (-1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**19
# md = 998244353
md = 10**9+7

n, m = LI()
to = [[] for _ in range(n)]
for _ in range(m):
    u, v = LI1()
    to[u].append(v)
    to[v].append(u)

pp = [-1]*n
for u in to[0]:
    for v in to[u]:
        if v == 0: continue
        if pp[v] == -1:
            pp[v] = u
        else:
            pp[v] = v+n

for u in range(1, n):
    if pp[u] == -1: continue
    for v in to[u]:
        if pp[v] != -1 and pp[v] != pp[u] and pp[v] != u and v != pp[u]:
            print("YES")
            exit()

print("NO")