n,m=map(int,input().split())
stations = [[] for i in range(n)]
ans =[0]*n

for i in range(m):
    a,b=map(int,input().split())
    stations[a].append(b)
    stations[b].append(a)
    ans[a] = 1
    ans[b] = 1
    if i == 0:start = a
    

cnt=0
for i in stations:
    if len(i)%2 == 1:
        cnt+=1

f=[0]*n
def  dfs(x):
    for i in stations[x]:
        if f[i] == 0:
            f[i] = 1
            dfs(i)
f[start] = 1
dfs(start)

if (f == ans) and (cnt == 0 or cnt == 2):
    print('YES')
else:
    print('NO')