import sys,collections
sys.setrecursionlimit(10**7)
def Is(): return [int(x) for x in sys.stdin.readline().split()]
def Ss(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def S(): return input()

n,m = Is()

mat = [[] for _ in range(n)]
for _ in range(m):
    a,b = Is()
    mat[a].append(b)
    mat[b].append(a)

visited = [False]*(n)
l = 0
def DFS(v,p,d):
    visited[v] = True
    for e in mat[v]:
        if e != p and d<=m:
            DFS(e, v,d+1)
DFS(0,0,0)

odd = 0 
for i,e in enumerate(mat):
    if len(e) > 0:
        if visited[i] == False:
            print("NO")
            exit()
        elif len(e) % 2 == 1:
            odd += 1

if odd <= 2:
    print("YES")
else:
    print("NO")