import sys
sys.setrecursionlimit(10 ** 6)
from collections import *
def MI(): return map(int, sys.stdin.readline().split())

def main():
    def dfs(u,pu=-1):
        res=1
        for cu in to[u]:
            if cu==pu:continue
            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()
    if odd==1 or odd>2 or dfs(root)!=sz:
        print("NO")
    else:
        print("YES")
        
main()