# coding: utf-8


def main():
    N, M = map(int, input().split())
    edges = [set() for _ in range(N)]
    for _ in range(M):
        a, b = map(int, input().split())
        edges[a-1].add(b-1)
        edges[b-1].add(a-1)

    # 頂点0から距離2の点,経由点の候補
    d2vs = [set() for _ in range(N)]
    for i in edges[0]:
        for j in edges[i]:
            d2vs[j].add(i)

    # (頂点0から距離2の点)から(頂点0から距離2の点)への辺があり、
    # 別の頂点を経由して行けることを確認
    for i in range(1, N):
        li = len(d2vs[i])
        if li == 0: continue
        for j in edges[i]:
            if j == 0: continue
            lj = len(d2vs[j])
            if lj == 0: continue
            if li == 1 and lj == 1:
                if d2vs[i].issubset(d2vs[j]) or \
                   tuple(d2vs[i])[0] == j:
                    continue
            return True

    return False


if main():
    print("YES")
else:
    print("NO")