graph g;
int n,a[1d5],b[1d5],c[2d5],z;
{
	rd(n,(a,b)(n));
	g.setEdge(n+1,n,a,b);
	g.bcc(c);
	rep(i,n){
		if(c[a[i]]==c[b[i]]){
			a[z++]=i+1;
		}
	}
	wt(z);
	wt(a(z));
}