/**
 *    author:  MaGnsi0
 *    created: 27.09.2023 19:16:48
**/
#include <bits/stdc++.h>

using namespace std;

const int OO = 2e9;

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    int n, m;
    cin >> n >> m;
    vector<vector<pair<int, int>>> adj(n);
    for (int i = 0; i < m; ++i) {
        int u, v, c;
        cin >> u >> v >> c;
        adj[u - 1].emplace_back(v - 1, c);
        adj[v - 1].emplace_back(u - 1, c);
    }
    vector<int> p(n, -1), d(n, OO), diff(n, 0);
    set<tuple<int, int, int, int, int>> S;
    d[0] = 0, diff[0] = -1 - OO, S.emplace(0, OO + 1, 0, -1, OO);
    while (!S.empty()) {
        int d_v, diff_v, v, maxe, mine;
        tie(d_v, diff_v, v, maxe, mine) = *S.begin();
        S.erase(S.begin());
        diff_v *= -1;
        if (d_v != d[v] || diff_v != diff[v]) {
            continue;
        }
        for (auto [u, c] : adj[v]) {
            if (d_v + 1 < d[u]) {
                p[u] = v;
                d[u] = d_v + 1;
                diff[u] = max(maxe, c) - min(mine, c);
                S.emplace(d[u], -diff[u], u, max(maxe, c), min(mine, c));
            } else if (d_v + 1 == d[u] && diff[u] < max(maxe, c) - min(mine, c)) {
                p[u] = v;
                d[u] = d_v + 1;
                diff[u] = max(maxe, c) - min(mine, c);
                S.emplace(d[u], -diff[u], u, max(maxe, c), min(mine, c));
            }
        };
    }
    cout << d[n - 1] << "\n";
    vector<int> path;
    for (int v = n - 1; v != -1; v = p[v]) {
        path.push_back(v);
    }
    reverse(path.begin(), path.end());
    for (int v : path) {
        cout << v + 1 << " ";
    }
}