import sys
sys.setrecursionlimit(10 ** 8)

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

s = set()
parent = [-1] * N
def find(i):
    if parent[i] < 0:return i
    parent[i] = find(parent[i])
    return parent[i]
def unite(i,j):
    I = find(i)
    J = find(j)
    if I == J:return False
    parent[J] += parent[I]
    parent[I] = J
    return True
memo = [0] * N
t = -1
for _ in range(M):
    a,b = map(int,input().split())
    memo[a] ^= 1
    memo[b] ^= 1
    s.add(a)
    s.add(b)
    unite(a,b)
    t = b
S = sum(memo)
if len(s) == -parent[find(t)] and S <= 2:
    print('YES')
else:
    print('NO')