#include<vector>
#include <string>
#include<algorithm>
#include <iostream>
#include <queue>
#include<set>
#include<cmath>
#include<math.h>
using namespace std;
#define ll long long
#define pll pair<long long, long long>
#define mp make_pair
#define pb push_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define cin(a) for(ll ghgh = 0; ghgh<a.size(); ghgh++) cin»a[ghgh];
#define pcin(a) for(ll ghgh = 0; ghgh<a.size(); ghgh++) cin»a[ghgh].first»a[ghgh].second;
#define cout(a) for(ll ghgha = 0; ghgha<a.size(); ghgha++) cout<<a[ghgha]<<" ";
#define pcout(a) for(ll ghgha = 0; ghgha<a.size(); ghgha++) cout«a[ghgha].first«" "«a[ghgha].second«endl;
const ll inf = 1e9 + 7, llinf = 1e18 + 123;
void xru() {
    setlocale(LC_ALL, "rus");
    /*freopen(".in", "r", stdin);
    freopen(".out", "w", stdout);*/
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
}






int main()
{
 xru();

 ll n, m;
 cin >> n >> m;
 vector<vector<ll>>check(n, vector<ll>(n, llinf));
 vector<ll>x(m), y(m), cnt(m);
 for (ll i = 0; i < m; i++) {
     cin >> x[i] >> y[i] >> cnt[i];
     x[i]--, y[i]--;
     if (x[i] == y[i]) continue;
     check[x[i]][y[i]] = min(check[ x[i] ][ y[i] ], cnt[i]);
     check[y[i]][x[i]] = check[x[i]][y[i]];
 }
 vector < vector<pll>>g(n);
 for (ll i = 0; i < m; i++) {
     if (x[i] == y[i] || check[x[i]][y[i]] == llinf) continue;
     g[x[i]].push_back({ y[i], check[x[i]][y[i]] });
     g[y[i]].push_back({ x[i], check[x[i]][y[i]] });
     check[x[i]][y[i]] = llinf;
     check[y[i]][x[i]] = llinf;

 }
 vector<pll>prev(n, { -1, inf });
 vector<ll>dist(n, inf);
 vector<bool>used(n, false);
 queue<ll>q;
 vector<vector<pll>> lg(n);
 q.push(n - 1);
 dist[n - 1] = 0;
 used[n - 1] = true;
 while (!q.empty()) {
     ll v = q.front();
     q.pop();
     for (ll i = 0; i < g[v].size(); i++) {
         pll to = g[v][i];
         if (!used[to.first]) {
             dist[to.first] = dist[v] + 1;
             lg[to.first].push_back({ v, to.second });
             lg[v].push_back(to);
             used[to.first] = true;
             q.push(to.first);
         }
         else {
             if (dist[v] + 1 == dist[to.first]) {
                 lg[to.first].push_back({ v, to.second });
                 lg[v].push_back(to);
             }
         }
     }
 }
 queue<ll>lq;
 vector<ll>minLdist(dist[0] + 1, inf);
 vector<ll>ldist(n, inf);
 vector<bool>lused(n, false), vlused(n, false);
 vector<ll>ans;
 ldist[0] = 0;
 lused[0] = true;
 lq.push(0);
 while (!lq.empty()) {
     ll lv = lq.front();
    // cout << lv << endl;
     lq.pop();
     if (!vlused[lv]) {
         //cout << lv << " ";
         for (ll i = 0; i < lg[lv].size(); i++) {
             pll lto = lg[lv][i];
             if (!lused[lto.first]) {
                 minLdist[ ldist[lv] + 1 ] = min( minLdist[ldist[lv] + 1] , lto.second );

             }
             else {
                 if (ldist[lv] + 1 == ldist[lto.first]) {
                     minLdist[ldist[lv] + 1] = min(minLdist[ldist[lv] + 1], lto.second);

                 }

             }
         }
         vlused[lv] = true;
         lq.push(lv);
     }
     else {
         for (ll i = 0; i < lg[lv].size(); i++) {
             pll lto = lg[lv][i];
             if (!lused[lto.first]) {
                 ldist[lto.first] = ldist[lv] + 1;
                 lused[lto.first] = true;
                 if (lto.second == minLdist[ldist[lto.first]]) {
                     lq.push(lto.first);
                 }
             }
         }
     }

 }

 cout << minLdist.size() - 1<<endl;
 for (ll i = 1; i < minLdist.size(); i++) {
     cout << minLdist[i] << " ";
 }



}