n,m = map(int,input().split())
g = [set() for _ in range(n)]
for i in range(m):
    a,b = map(int,input().split())
    g[a-1].add(b-1)
    g[b-1].add(a-1)
    
size = [0]*n
res = [None]*n
for i in range(1,n):
    s = g[0]&g[i]
    if len(s) >= 3:
        size[i] = 3
    else:
        size[i] = len(s)
        res[i] = s

for a in range(1,n):
    if size[a] == 0: continue
    for b in g[a]:
        if b==0 or size[b] == 0: continue
        if size[a] >= 3 or size[b] >= 3:
            print("YES")
            exit()
        for c in res[a]:
            for d in res[b]:
                if c != d and b != c and a != d:
                    print("YES")
                    exit()
print("NO")