#define I for(i=m;i--;)
int i,m,a[50000],b[50000],c[20000],d[20000],e,f;main(n){scanf("%d%d",&n,&m);I scanf("%d%d",a+i,b+i),c[--b[i]]|=!--a[i],c[a[i]]|=!b[i];I{if(a[i]*c[b[i]])d[a[i]]=d[a[i]]?--f:b[i];if(b[i]*c[a[i]])d[b[i]]=d[b[i]]?--f:a[i];}I e|=d[a[i]]&&d[b[i]]&&d[a[i]]-b[i]&&d[b[i]]-a[i]&&d[a[i]]-d[b[i]];i=!puts(e?"YES":"NO");}