def is_valid(c, d, bs):
    b = bs[c] - {d}
    e = bs[d] - {c}
    return b and e and len(b | e) >= 2
N, M = map(int, input().split())
Es = [set() for i in range(N)]
for i in range(M):
    a, b = map(int, input().split())
    Es[a-1].add(b-1)
    Es[b-1].add(a-1)
d1 = Es[0]
d2 = set()
for d in d1: d2 |= Es[d]
d2 -= {0}
bs = [d1 & Eb for Eb in Es]
for c in d2:
    for d in Es[c]:
        if d in d2 and is_valid(c, d, bs):
            print("YES")
            break
    else:continue
    break
else:print("NO")