割点判断（tarjan）

/*
    割点判断
    tarjan
    by sbn
*/
#include<iostream>
#include<cstdio>
using namespace std;
struct node{
        int x,y,nxt;
        node(){}
        node(int nx,int ny,int nnxt){
                x=nx;y=ny;nxt=nnxt;
        }
}tree[400001];
int head[400001],cnt_e,n,m,dep;
int dfn[400001],low[400001],root;
bool flag[400001];
void build(int x,int y){
        tree[++cnt_e]=node(x,y,head[x]);
        head[x]=cnt_e;
        tree[++cnt_e]=node(y,x,head[y]);
        head[y]=cnt_e;
}
void dfs(int u,int f){
        dep++;
        int child=0;
        dfn[u]=low[u]=dep;
        int z=head[u];
        while (z){
                if (dfn[tree[z].y]<=0){
                    child++;
                    dfs(tree[z].y,u);
                    low[u]=min(low[u],low[tree[z].y]);
                    if (u!=root&&dfn[u]<=low[tree[z].y])    flag[u]=1;
                    if (u==root&&child>1)   flag[u]=1;
                }
                else{
                    if (tree[z].y!=f)   low[u]=min(low[u],dfn[tree[z].y]);
                }
                z=tree[z].nxt;
        }
}
int main(){
    //freopen("gedianpanduan.in","r",stdin);
    cin>>n>>m;
    for (int i=1;i<=m;i++){
            int a,b;
            cin>>a>>b;
            build(a,b);
    }

    for (int i=1;i<=n;i++)if (head[i]!=0){root=i;break;}

    dfs(root,1);
    int num=0;
    for (int i=1;i<=n;i++)if (flag[i])  num++;
    cout<<num<<endl;
    for (int i=1;i<=n;i++)if (flag[i])  cout<<i<<" ";
    return 0;
}