#include<iostream>

 #include<cstdio>

 #include<algorithm>

 #include<cmath>

 #include<cstring>

 #include<cstdlib>

 #include<set>

 #include<map>

 #include<vector>

 #include<stack>

 #include<queue>

 #define ll long long

 #define inf 2147383611

 #define MAXN 100100

 #define MOD 5050

 using namespace std;

 inline int read()

 {

     int x=,f=;

     char ch;ch=getchar();

     while(!isdigit(ch)) {if(ch=='-') f=-;ch=getchar();}

     while(isdigit(ch)) {x=x*+ch-'';ch=getchar();}

     return x*f;

 }

 int n,m,next[MAXN*],first[MAXN],to[MAXN*],cnt;

 int scc,dfn[MAXN],low[MAXN],bl[MAXN],stp,num[MAXN],minn[MAXN];

 bool vis[MAXN];

 int st[MAXN],top;

 void add(int u,int v) {next[++cnt]=first[u],first[u]=cnt,to[cnt]=v;}

 void tarjan(int x)

 {

     low[x]=dfn[x]=++stp,st[++top]=x,vis[x]=;

     for(int i=first[x];i;i=next[i])

     {

         if(!dfn[to[i]])

         {

             tarjan(to[i]);low[x]=min(low[x],low[to[i]]);

         }

         else if(vis[to[i]]) low[x]=min(low[x],dfn[to[i]]);

     }

     if(low[x]==dfn[x])

     {

         scc++,minn[scc]=inf;

         while(st[top+]!=x) minn[scc]=min(st[top],minn[scc]),bl[st[top]]=scc,num[scc]++,vis[st[top]]=,top--;

     }

 }

 int main()

 {

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

     int t,a,b;

     while(m--)

     {

         a=read(),b=read(),t=read();

         if(t==) add(a,b);

         else {add(a,b);add(b,a);}

     }

     for(int i=;i<=n;i++) if(!dfn[i]) tarjan(i);

     int tmp=,k;

     for(int i=;i<=scc;i++) if(num[i]>=tmp||(num[i]==tmp&&minn[i]<minn[tmp])) tmp=num[i],k=i;

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

     for(int i=;i<=n;i++) if(bl[i]==k) printf("%d ",i);

 }