import sre_constants import sys sys.setrecursionlimit(200005) int1 = lambda x: int(x)-1 p2D = lambda x: print(*x, sep="\n") def II(): return int(sys.stdin.readline()) def LI(): return list(map(int, sys.stdin.readline().split())) def LI1(): return list(map(int1, sys.stdin.readline().split())) def LLI(rows_number): return [LI() for _ in range(rows_number)] def LLI1(rows_number): return [LI1() for _ in range(rows_number)] def SI(): return sys.stdin.readline().rstrip() # dij = [(0, 1), (-1, 0), (0, -1), (1, 0)] dij = [(0, 1), (1, 0), (0, -1), (-1, 0)] # dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)] inf = 10**19 # md = 998244353 md = 10**9+7 n, m = LI() to = [[] for _ in range(n)] for _ in range(m): u, v = LI1() to[u].append(v) to[v].append(u) pp = [-1]*n for u in to[0]: for v in to[u]: if v == 0: continue if pp[v] == -1: pp[v] = u else: pp[v] = v+n for u in range(1, n): if pp[u] == -1: continue for v in to[u]: if pp[v] != -1 and pp[v] != pp[u]: print("YES") exit() print("NO")