#include <algorithm>

#include  <iterator>

#include  <iostream>

#include   <cstring>

#include   <cstdlib>

#include   <iomanip>

#include    <bitset>

#include    <cctype>

#include    <cstdio>

#include    <string>

#include    <vector>

#include     <stack>

#include     <cmath>

#include     <queue>

#include      <list>

#include       <map>

#include       <set>

#include   <cassert>

using namespace std;

#define lson (l , mid , rt << 1)

#define rson (mid + 1 , r , rt << 1 | 1)

#define debug(x) cerr << #x << " = " << x << "\n";

#define pb push_back

#define pq priority_queue

typedef long long ll;

typedef unsigned long long ull;

//typedef __int128 bll;

typedef pair<ll ,ll > pll;

typedef pair<int ,int > pii;

typedef pair<int,pii> p3;

//priority_queue<int> q;//这是一个大根堆q

//priority_queue<int,vector<int>,greater<int> >q;//这是一个小根堆q

#define fi first

#define se second

//#define endl '\n'

#define OKC ios::sync_with_stdio(false);cin.tie(0)

#define FT(A,B,C) for(int A=B;A <= C;++A)  //用来压行

#define REP(i , j , k)  for(int i = j ; i <  k ; ++i)

#define max3(a,b,c) max(max(a,b), c);

#define min3(a,b,c) min(min(a,b), c);

//priority_queue<int ,vector<int>, greater<int> >que;

const ll oo = 1ll<<;

const ll mos = 0x7FFFFFFF;  //

const ll nmos = 0x80000000;  //-2147483648

const int inf = 0x3f3f3f3f;

const ll inff = 0x3f3f3f3f3f3f3f3f; //

const int mod = ;

const double esp = 1e-;

const double PI=acos(-1.0);

const double PHI=0.61803399;    //黄金分割点

const double tPHI=0.38196601;

template<typename T>

inline T read(T&x){

    x=;int f=;char ch=getchar();

    while (ch<''||ch>'') f|=(ch=='-'),ch=getchar();

    while (ch>=''&&ch<='') x=x*+ch-'',ch=getchar();

    return x=f?-x:x;

}

/*-----------------------showtime----------------------*/

            const int maxn = 1e5+;

            struct E{

                int u,v;

                int nxt;

            }edge[maxn];

            int head[maxn],gtot = ;

            void addedge(int u,int v){

                edge[gtot].u = u;

                edge[gtot].v = v;

                edge[gtot].nxt = head[u];

                head[u] = gtot++;

            }

            priority_queue<int,vector<int>,greater<int> >tmp,ans;//这是一个小根堆q

            int vis[maxn],dfn[maxn],low[maxn];

            stack<int>sk;

            int tot = ;

            void tarjan(int u){

                tot++;

                dfn[u] = low[u] = tot;

                vis[u] = ; sk.push(u);

                for(int i=head[u]; ~i; i = edge[i].nxt){

                    int v = edge[i].v;

                    if(dfn[v] == ) {

                        tarjan(v);

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

                    }

                    else if(vis[v]){

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

                    }

                }

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

                    while(!tmp.empty())tmp.pop();

                    while(!sk.empty() && sk.top() != u){

                        vis[sk.top()] = ;

                        tmp.push(sk.top()); sk.pop();

                    }

                    vis[sk.top()] = ;

                    tmp.push(sk.top()); sk.pop();

                    if(tmp.size() > ans.size()) ans = tmp;

                    else if(tmp.size() == ans.size() && tmp.top() < ans.top()) ans = tmp;

                }

            }

 int main(){

            int n,m;

            scanf("%d%d", &n, &m);

            memset(head, -, sizeof(head));

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

                int u,v,op;

                scanf("%d%d%d", &u, &v, &op);

                if(op == ) addedge(u,v);

                else {

                    addedge(u,v);

                    addedge(v,u);

                }

            }

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

              if(dfn[i] == )tarjan(i);

            printf("%d\n", (int)ans.size());

            while(!ans.empty()){

                printf("%d ", ans.top());

                ans.pop();

            }

            puts("");

            return ;

 }