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

stn_list = [[] for i in range(N)]
stn_count = [0 for i in range(N)]

def checklink(n):
    if stn_list[n]==[]:
        return
    target = stn_list[n][:]
    stn_list[n] = []
    for i in target:
        checklink(i)

for i in range(M):
    s,t = map(int,input().split())
    stn_list[s].append(t)
    stn_list[t].append(s)
    stn_count[s] += 1
    stn_count[t] += 1

checklink(s)

for i in stn_list:
    if i != []:
        print("NO")
        exit(0)

count = 0
for i in range(N):
    if i%2 == 1:
        count += 1
        if count>2:
            print("NO")
            exit(0)
print("YES")