import sys
sys.setrecursionlimit(10 ** 6)
from itertools import *
from bisect import *
# from math import *
from collections import *
from heapq import *
from random import *
from decimal import *
import numpy as np

int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def MI1(): return map(int1, sys.stdin.readline().split())
def MF(): return map(float, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LF(): return list(map(float, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
dij = [(0, 1), (1, 0), (0, -1), (-1, 0)]

def main():
    def dfs(u,pu=-1):
        res=1
        for cu in to[u]:
            if cu==pu:continue
            if vis[cu]:continue
            vis[cu]=True
            res+=dfs(cu,u)
        return res

    to=defaultdict(list)
    n,m=MI()
    ss=set()
    for _ in range(m):
        a,b=MI()
        to[a].append(b)
        to[b].append(a)
        ss.add(a)
        ss.add(b)
    odd=sum(len(x)%2 for x in to.values())
    sz=len(ss)
    root=ss.pop()
    vis=[False]*n
    vis[root]=True
    if odd==1 or odd>2 or dfs(root)!=sz:
        print("NO")
    else:
        print("YES")

main()