from collections import Counter
from scipy.sparse.csgraph import connected_components
from scipy.sparse import csr_matrix

N, M = map(int, input().split())

deg = [0] * N
valid_stations = set()
frm, to = [], []
for _ in range(M):
    a, b = map(int, input().split())
    valid_stations.add(a)
    valid_stations.add(b)
    frm.append(a)
    to.append(b)
    deg[a] += 1
    deg[b] += 1

# 連結判定
matr = csr_matrix(([1] * M, (frm, to)), shape=(N, N))
_, labels = connected_components(matr)
ct = Counter(labels[list(valid_stations)])
if len(ct) > 1:
    print('NO')
    exit()

# 一筆書き可能性判定
is_odd = 0
for x in deg:
    if x % 2:
        is_odd += 1
print('YES' if is_odd in (0, 2) else 'NO')