from collections import defaultdict

n, m = map(int, input().split())
Edge = defaultdict(list)
for _ in range(m):
    u, v = map(int, input().split())
    u -= 1
    v -= 1
    Edge[u].append(v)
    Edge[v].append(u)
Stack = [u]
seen = set([u])
while Stack:
    cp = Stack.pop()
    for np in Edge[cp]:
        if np in seen:
            continue
        seen.add(np)
        Stack.append(np)

odd_n = 0
for i in range(n):
    if i not in seen and Edge[i]:
        print("NO")
        exit()
    if len(Edge[i]) % 2 == 1:
        odd_n += 1
if odd_n <= 2:
    print("YES")
else:
    print("NO")