#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include <cmath>

 #include<stack>

 #include<vector>

 #include<map>

 #include<set>

 #include<queue>

 #include<algorithm>

 using namespace std;

 typedef long long LL;

 const int INF = ;

 const int mod=;

 const int maxn=;

 struct Edge{

     int u,v,c;

     Edge(int u=,int v=,int c=):u(u),v(v),c(c){}

 };

 vector<Edge> edges;

 vector<int> G[maxn];

 void addedges(int u,int v,int c){

     edges.push_back(Edge(u,v,c));

     int idx=edges.size()-;

     G[u].push_back(idx);

 }

 int n,vis[maxn],d[maxn];

 void rev_bfs(){//求出每一个节点到终点n-1的距离

     memset(vis,,sizeof(vis));

     vis[n-]=true;

     d[n-]=;

     queue<int> q;

     q.push(n-);

     while(!q.empty()){

         int v=q.front();q.pop();

         for(int i=;i<G[v].size();i++){

             int e=G[v][i];

             int u=edges[e].v;

             if(!vis[u]){

                 vis[u]=true;

                 d[u]=d[v]+;

                 q.push(u);

             }

         }

     }

 }

 vector<int> ans;

 void bfs(){

     memset(vis,,sizeof(vis));

     vis[]=true;

     ans.clear();

     vector<int> next;

     next.push_back();

     for(int i=;i<d[];i++){

         int min_color=INF;

         for(int j=;j<next.size();j++){

             int u=next[j];

             for(int k=;k<G[u].size();k++){

                 int e=G[u][k];

                 int v=edges[e].v;

                 if(d[u]==d[v]+)

                 min_color=min(min_color,edges[e].c);

             }

         }

         ans.push_back(min_color);

         vector<int> next2;

         for(int j=;j<next.size();j++){

             int u=next[j];

             for(int k=;k<G[u].size();k++){

                 int e=G[u][k];

                 int v=edges[e].v;

                 if(d[u]==d[v]+&&edges[e].c==min_color&&!vis[v]) {

                     vis[v]=true;

                     next2.push_back(v);

                 }

             }

         }

         next=next2;

     }

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

     printf("%d",ans[]);

     for(int i=;i<ans.size();i++) printf(" %d",ans[i]);

     printf("\n");

 } 

 int main(){

     int m,u,v,c;

     while(scanf("%d %d",&n,&m)==){

         edges.clear();

         for(int i=;i<n;i++) G[i].clear();

         while(m--){

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

             addedges(u-,v-,c);

             addedges(v-,u-,c);

         }

         rev_bfs();

         bfs();

     }

     return ;

 }