#yuki583
import sys

def dfs(u):
 if flg[u]==1:
  return 0
 flg[u]=1
 for i in xrange(n):
  if g[u][i]==1:
   dfs(i)

n,m=map(int,raw_input().split())
g=[[0]*n for i in xrange(n)]
flg={}
for i in xrange(m):
 a,b=map(int,raw_input().split())
 g[a][b]+=1
 g[b][a]+=1
 flg[a]=0
 flg[b]=0
dfs(a)
for val in flg.values():
 if val==0:
  print 'NO'
  sys.exit()
cnt=0
for i in xrange(n):
 if g[i].count(1)%2==1:
  cnt+=1
  if cnt>2:
   print 'NO'
   sys.exit()
print 'YES'