/*
    luogu P1726 上白泽慧音
    
    Tarjan求强连通分量
     
    输出最大强联通分量是什么 
     
*/
#include <algorithm>
#include <cstdio>
#include <stack>

#define Max 5020
#define INF 1e7

void read (int &now)
{
    now = 0;
    char word = getchar ();
    while (word > ‘9‘ || word < ‘0‘)
        word = getchar ();
    while (word >= ‘0‘ && word <= ‘9‘)
    {
        now = now * 10 + word - ‘0‘;
        word = getchar ();
    }
}

struct Edge
{
    int to;        
    int next;
};
    
int Count;
int Saber;
    
std :: stack <int> Stack;

struct Road
{
    int edge[Max];
    int Count;    
};

Road road[Max];

Edge edge[Max << 6];
    
int Edge_Count;
int edge_list[Max];
    
inline void AddEdge (int from, int to)
{
    Edge_Count++;
    edge[Edge_Count].to = to;
    edge[Edge_Count].next = edge_list[from];
    edge_list[from] = Edge_Count;
}
    
int father[Max];
int low[Max];
int ruri[Max];

void Dfs (int now)
{
    father[now] = ++Count;
    low[now] = Count;
    Stack.push (now);
    for (int i = edge_list[now]; i; i = edge[i].next)
        if (!father[edge[i].to])
        {
            Dfs (edge[i].to);
            low[now] = low[edge[i].to] < low[now] ? low[edge[i].to] : low[now];
        }
        else if (!ruri[edge[i].to])
            low[now] = father[edge[i].to] < low[now] ? father[edge[i].to] : low[now];
    int x;
    if (low[now] == father[now])
    {
        Saber++;
        x = now + 1;
        while (x != now)
        {
            x = Stack.top ();
            Stack.pop ();
            ruri[x] =  Saber;
            road[Saber].edge[++road[Saber].Count] = x;
        }
    }
}

int N, M;

int main (int argc, char *argv[])
{
    read (N);
    read (M);
    int x, y;
    int type;
    int Max_Number = 0;
    int Min_Edge;
    
    for (register int i = 1; i <= M; i++)
    {
        read (x);
        read (y);
        read (type);
        AddEdge (x, y); 
        if (type == 2)
            AddEdge (y, x);    
    }
    int Answer_Count;
    for (int i = 1; i <= N; i++)
        if (!father[i])
            Dfs (i);
    for (int i = 1; i <= Saber; i++)
        std :: sort (road[i].edge + 1, road[i].edge + 1 + road[i].Count);
    int pos;
    for (int i = 1; i <= Saber; i++)
    {
        if (road[i].Count > Max_Number)
        {
            Max_Number = road[i].Count;
            Min_Edge = road[i].edge[1];
            pos = i;
        }
        else if (road[i].edge[1] < Min_Edge && road[i].Count == Max_Number)
        {
            Min_Edge = road[i].edge[1];
            pos = i;
        }
    }
    printf ("%d\n", road[pos].Count);
    for (int i = 1; i <= road[pos].Count; i++)
        printf ("%d ", road[pos].edge[i]);
    return 0;
}