n,m = map(int,raw_input().split())

class UnionFind():
    def __init__(self,size):
        self.table = [-1 for _  in range(size)]

    def find(self,x):
        while self.table[x] >= 0:
            x = self.table[x]
        return x

    def union(self,x,y):
        s1 = self.find(x)
        s2 = self.find(y)
        if s1 != s2:
            if self.table[s1] != self.table[s2]:
                if self.table[s1] < self.table[s2]:
                    self.table[s2] = s1
                else:
                    self.table[s1] = s2
            else:
                self.table[s1] += -1
                self.table[s2] = s1
        return

degree = [0 for i in range(n)]
uf = UnionFind(n)
for i in range(m):
	f,t = map(int,raw_input().split())
	degree[f] += 1; degree[t] += 1

	uf.union(f,t)
a = -1
for i in range(n):
	if degree[i] > 0:
		a = i
		break

a = uf.find(a)

count = 0
for i in range(n):
	
	if degree[i] != 0 and uf.find(i) == a:
		if degree[i] % 2 == 1:
			count += 1
	elif degree[i] == 0:
		continue
	else: 
		print 'NO'
		quit()

if count == 0 or count == 2:
	print 'YES'
else :
	print 'NO'