435ertert

#include <iostream>
#include <vector>
#include <utility>
#include <limits>
#include <map>
#include <set>
#include <deque>

constexpr auto Inf = std::numeric_limits <int64_t>::max ();
using Ip = std::pair <int, int>;
using VIp = std::vector <Ip>;
using VVIp = std::vector <VIp>;
using Vi = std::vector <int>;
using Vi64 = std::vector <int64_t>;
using STi = std::set <int>;
using Hsi64i = std::map <int64_t, int>;
using DQi = std::deque <int>;


int n, m, u, v, w;
VVIp Graph, TGraph;
Vi64 DistanceX, DistanceY;
Vi Tag;
DQi DQ;
Hsi64i Hash;
STi Store;


inline void DEsopoPape (const int& src, Vi64& Distance, const VVIp& Graph) {
    Tag.assign (n + 1, 2);
    DQ.push_back (src), Distance[src] = 0LL;
    while (!DQ.empty ()) {
        int u = DQ.front ();
        DQ.pop_front (), Tag[u] = 0;
        for (const auto& e: Graph[u])
            if (Distance[e.first] > Distance[u] + e.second) {
                Distance[e.first] = Distance[u] + e.second;
                if (Tag[e.first] == 2)
                    Tag[e.first] = 1, DQ.push_back (e.first);
                else if (!Tag[e.first])
                    Tag[e.first] = 1, DQ.push_front (e.first);
            }
    }
}


int main () {
    std::cin >> n >> m;
    Graph.resize (n + 1), TGraph.resize (n + 1);
    DistanceX.assign (n + 1, Inf), DistanceY.assign (n + 1, Inf);
    for (int i = 1; i <= m; ++ i)
        std::cin >> u >> v >> w,
        Graph[u].emplace_back (std::make_pair (v, w)),
        TGraph[v].emplace_back (std::make_pair (u, w));

    DEsopoPape (1, DistanceX, Graph), DEsopoPape (n, DistanceY, TGraph);
    for (int u = 1; u <= n; ++ u)
        if (DistanceX[n] == DistanceX[u] + DistanceY[u])
            ++ Hash[DistanceX[u]];
    for (int u = 1; u <= n; ++ u)
        if (DistanceX[n] == DistanceX[u] + DistanceY[u] && Hash[DistanceX[u]] == 1)
            Store.insert (u);

    std::cout << Store.size () << "\n";
    for (const auto& u: Store)
        std::cout << u << " ";

    return 0;
}