#include<bits/stdc++.h>
using namespace std;
const int inf=1e6+5;
int r,cnt,sum,vis[inf],f[inf],ans,low[inf],dfn[inf],head[inf],d[inf];
stack<int>s;
struct node{
    int to,next;
}e[inf];

void add(int x,int y)
{
    e[++cnt]={y,head[x]};
    head[x]=cnt;
}
void tarjan(int x)
{
    low[x]=dfn[x]=++sum;
    s.push(x);
    vis[x]=1;
    for(int i=head[x];i;i=e[i].next)
    {
        int to=e[i].to;
        if(!dfn[to])
        {
            tarjan(to);
            low[x]=min(low[x],low[to]);
        }
        else
            low[x]=min(low[x],dfn[to]);
        if(dfn[x]==low[x]) {
            ans++;
            int y;
            do {
                y=s.top();
                s.pop();
                f[y]=ans;
                d[ans]++;
            vis[y]=0;
            } while (x != y);
        }
    }

}

int main()
{
    int n,m,a,b,t;
    cin>>n>>m;
    for(int i=1;i<=n;i++) {
        cin >> a >> b >> t;
        add(a, b);
        if (t == 2)
            add(b, a);
    }
    for(int i=1;i<=n;i++)
        if(!dfn[i])tarjan(i);

        for(int i=1;i<=ans;i++)
            r=max(r,d[i]);

        cout<<r<<endl;
        for(int i=1;i<=n;i++)
            if(d[f[i]]==ans)
                cout<<i<<" ";
            return 0;
}