#include<iostream>

#include<cstring>

#include<cstdio>

#define N 5010

#define M 100010

int n,m,Head[N],Enum,stack[N],top,ms;

int dfn[N],cnt,low[N],belong[N],size[N],num;

bool ins[N];

struct NODE{

    int to,next;

} e[M];

inline void add(int x,int y){

    e[++Enum].to=y;

    e[Enum].next=Head[x];

    Head[x]=Enum;

}

inline int read(){

    int x=; char c=getchar();

    while(c<''||c>'') c=getchar();

    while(''<=c&&c<='') { x=(x<<)+(x<<)+c-''; c=getchar(); }

    return x;

}

inline void Tarjan(int u){

    dfn[u]=low[u]=++cnt;

    ins[u]=; stack[++top]=u;

    for(int i=Head[u];i;i=e[i].next){

        int v=e[i].to;

        if(!dfn[v]){

            Tarjan(v);

            low[u]=std::min(low[u],low[v]);

        }

        else if(ins[v])

            low[u]=std::min(low[u],dfn[v]);

    }

    if(low[u]==dfn[u]){

        belong[u]=++num;

        while(stack[top]!=u){

            int k=stack[top];

            belong[k]=num;

            size[num]++;

            ins[k]=;

            top--;

        } size[num]++;

        top--; ins[u]=;

    }

}

int main()

{

    n=read(); m=read();

    int x,y,t;

    for(int i=;i<=m;i++){

        x=read(); y=read(); t=read();

        add(x,y); if(t==) add(y,x);

    }

    for(int i=;i<=n;i++)

     if(!dfn[i]) Tarjan(i);

    for(int i=;i<=num;i++)

     if(size[i]>ms) ms=size[i];

    int ans;

    for(int i=;i<=n;i++)

     if(size[belong[i]]==ms){

         ans=belong[i];

         break;

     }

    printf("%d\n",ms);

    for(int i=;i<=n;i++)

     if(belong[i]==ans)

      printf("%d ",i);

    puts("");

    return ;

}