N,M = map(int,input().split())
l = [[] for _ in range(N)]
vis = [0 for _ in range(N)]

for _ in range(M):
    Sa,Sb = map(int,input().split())
    l[Sa].append(Sb)
    l[Sb].append(Sa)
    vis[Sa] += 1
    vis[Sb] += 1

def dfs(x):
    if l[x] == []:
        return
    z = l[x][:]
    l[x] = []
    for y in z:
        dfs(y)

for i in range(N):
    if vis[i] > 0:
        dfs(i)
        break
flg = True
for i in range(N):
    if vis[i] > 0 and l[i] != []:
        flg = False
        break
ans = "NO"
if flg and [x%2 for x in vis].count(1) in [0,1,2]:
    ans = "YES"

print(ans)