import sys
from sys import stdin
from collections import defaultdict

def main():
    N, M = map(int, stdin.readline().split())
    adj = defaultdict(set)
    for _ in range(M):
        a, b = map(int, stdin.readline().split())
        adj[a].add(b)
        adj[b].add(a)
    
    # Get neighbors of vertex 1
    S = adj.get(1, set())
    if not S:
        print("NO")
        return
    
    S_set = S  # Using a set for O(1) lookups
    
    # Check all possible paths of the form 1 -> a -> b -> c -> d -> 1
    for a in S:
        for b in adj[a]:
            if b == 1:
                continue
            # b is a neighbor of a (excluding 1)
            for c in adj[b]:
                if c == 1 or c == a:
                    continue
                # c is a neighbor of b (excluding 1 and a)
                for d in adj[c]:
                    if d == 1 or d == b:
                        continue
                    # d is a neighbor of c (excluding 1 and b)
                    if d in S_set and d != a and d != c:
                        print("YES")
                        return
    
    print("NO")

if __name__ == "__main__":
    main()