import sys
from sys import stdin

def main():
    sys.setrecursionlimit(1 << 25)
    n, m = map(int, stdin.readline().split())
    adj = [set() for _ in range(n + 1)]
    for _ in range(m):
        a, b = map(int, stdin.readline().split())
        adj[a].add(b)
        adj[b].add(a)
    # Collect neighbors of vertex 1
    U = adj[1]
    if len(U) < 2:
        print("NO")
        return
    # Check all possible u in U
    for u in U:
        for x in adj[u]:
            if x == 1:
                continue
            for y in adj[x]:
                if y in {u, x, 1}:
                    continue
                for v in adj[y]:
                    if v in {x, y}:
                        continue
                    if v in U and v != u:
                        print("YES")
                        return
    print("NO")

if __name__ == '__main__':
    main()