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

# UnionFind

Group = [i for i in range(N+1)] # グループ分け
Nodes = [1]*(N+1) # 各グループのノードの数

def find(x):
    while Group[x] != x:
        x=Group[x]
    return x

def Union(x,y):
    if find(x) != find(y):
        if Nodes[find(x)] < Nodes[find(y)]:
            
            Nodes[find(y)] += Nodes[find(x)]
            Nodes[find(x)] = 0
            Group[find(x)] = find(y)
            
        else:
            Nodes[find(x)] += Nodes[find(y)]
            Nodes[find(y)] = 0
            Group[find(y)] = find(x)

EDGE=[0]*(N+1)
USED=[0]*(N+1)

for i in range(M):
    x,y=map(int,input().split())
    Union(x,y)
    EDGE[x]+=1
    EDGE[y]+=1
    USED[x]=1
    USED[y]=1

f=USED.index(1)
for i in range(N+1):
    if USED[i]==1 and find(i)!=find(f):
        print("NO")
        exit()

ki=0
for x in EDGE:
    if x%2==1:
        ki+=1

if ki>=3:
    print("NO")
    exit()

print("YES")