import sys
from collections import defaultdict

def main():
    N, M = map(int, sys.stdin.readline().split())
    adj = defaultdict(list)
    for _ in range(M):
        a, b = map(int, sys.stdin.readline().split())
        adj[a].append(b)
        adj[b].append(a)
    
    # Get neighbors of vertex 1
    S = adj[1]
    if not S:
        print("NO")
        return
    
    S_set = set(S)
    
    # Check each neighbor u of 1
    for u in S:
        # Check all neighbors a of u (excluding 1)
        for a in adj[u]:
            if a == 1:
                continue
            # Check all neighbors b of a (excluding 1 and u)
            for b in adj[a]:
                if b == 1 or b == u:
                    continue
                # Check all neighbors x of b (excluding 1)
                for x in adj[b]:
                    if x == 1:
                        continue
                    # Check if x is a neighbor of 1 and distinct from u, a, b
                    if x in S_set and x != u and x != a and x != b:
                        print("YES")
                        return
    print("NO")

if __name__ == "__main__":
    main()