Language: C++

#include <bits/stdc++.h>
#pragma GCC diagnostic ignored "-Wsign-compare"
#pragma GCC diagnostic ignored "-Wsign-conversion"
#define NDEBUG
#define SHOW(...) static_cast<void>(0)
//!===========================================================!//
//!  dP     dP                          dP                    !//
//!  88     88                          88                    !//
//!  88aaaaa88a .d8888b. .d8888b. .d888b88 .d8888b. 88d888b.  !//
//!  88     88  88ooood8 88'  '88 88'  '88 88ooood8 88'  '88  !//
//!  88     88  88.  ... 88.  .88 88.  .88 88.  ... 88        !//
//!  dP     dP  '88888P' '88888P8 '88888P8 '88888P' dP        !//
//!===========================================================!//
using ld = long double;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
constexpr unsigned int MOD = 1000000007;
template <typename T>
constexpr T INF = std::numeric_limits<T>::max() / 4;
template <typename F>
constexpr F PI = static_cast<F>(3.1415926535897932385);
std::mt19937 mt{std::random_device{}()};
template <typename T>
bool chmin(T& a, const T& b) { return a = std::min(a, b), a == b; }
template <typename T>
bool chmax(T& a, const T& b) { return a = std::max(a, b), a == b; }
template <typename T>
std::vector<T> Vec(const std::size_t n, T v) { return std::vector<T>(n, v); }
template <class... Args>
auto Vec(const std::size_t n, Args... args) { return std::vector<decltype(Vec(args...))>(n, Vec(args...)); }
template <typename T>
constexpr T popCount(const T u)
{
#ifdef __has_builtin
    return u == 0 ? T(0) : (T)__builtin_popcountll(u);
#else
    unsigned long long v = static_cast<unsigned long long>(u);
    return v = (v & 0x5555555555555555ULL) + (v >> 1 & 0x5555555555555555ULL), v = (v & 0x3333333333333333ULL) + (v >> 2 & 0x3333333333333333ULL), v = (v + (v >> 4)) & 0x0F0F0F0F0F0F0F0FULL, static_cast<T>(v * 0x0101010101010101ULL >> 56 & 0x7f);
#endif
}
template <typename T>
constexpr T log2p1(const T u)
{
#ifdef __has_builtin
    return u == 0 ? T(0) : T(64 - __builtin_clzll(u));
#else
    unsigned long long v = static_cast<unsigned long long>(u);
    return v = static_cast<unsigned long long>(v), v |= (v >> 1), v |= (v >> 2), v |= (v >> 4), v |= (v >> 8), v |= (v >> 16), v |= (v >> 32), popCount(v);
#endif
}
template <typename T>
constexpr T clog(const T v) { return v == 0 ? T(0) : log2p1(v - 1); }
template <typename T>
constexpr T msbp1(const T v) { return log2p1(v); }
template <typename T>
constexpr T lsbp1(const T v)
{
#ifdef __has_builtin
    return __builtin_ffsll(v);
#else
    return v == 0 ? T(0) : popCount((v & (-v)) - T(1)) + T(1);
#endif
}
template <typename T>
constexpr bool ispow2(const T v) { return popCount(v) == 1; }
template <typename T>
constexpr T ceil2(const T v) { return v == 0 ? T(1) : T(1) << log2p1(v - 1); }
template <typename T>
constexpr T floor2(const T v) { return v == 0 ? T(0) : T(1) << (log2p1(v) - 1); }
//!=======================================================================================!//
//!   a88888b.                     dP       .88888.                             dP        !//
//!  d8'   '88                     88      d8'   '88                            88        !//
//!  88        .d8888b. .d8888b. d8888P    88        88d888b. .d8888b. 88d888b. 88d888b.  !//
//!  88        88'  '88 Y8ooooo.   88      88   YP88 88'  '88 88'  '88 88'  '88 88'  '88  !//
//!  Y8.   .88 88.  .88       88   88      Y8.   .88 88       88.  .88 88.  .88 88    88  !//
//!   Y88888P' '88888P' '88888P'   dP       '88888'  dP       '88888P8 88Y888P' dP    dP  !//
//!                                                                    88                 !//
//!                                                                    dP                 !//
//!=======================================================================================!//
template <typename T>
struct CostGraph
{
    CostGraph(const std::size_t v) : V{v}, edge(v), rev_edge(v) {}
    void addEdge(const std::size_t from, const std::size_t to, const T cost, const bool bi = false)
    {
        assert(from < V), assert(to < V);
        edge[from].push_back(Edge{to, cost}), rev_edge[to].push_back(Edge(from, cost));
        if (bi) { addEdge(to, from, cost, false); }
    }
    struct Edge
    {
        Edge(const std::size_t to, const T cost) : to{to}, cost{cost} {}
        const std::size_t to;
        const T cost;
        bool operator<(const Edge& e) const { return cost != e.cost ? cost < e.cost : to < e.to; }
    };
    const std::vector<Edge>& operator[](const std::size_t i) const { return assert(i < V), edge[i]; }
    friend std::ostream& operator<<(std::ostream& os, const CostGraph& g)
    {
        os << "[\n";
        for (std::size_t i = 0; i < g.V; i++) {
            for (const auto& e : g.edge[i]) { os << i << "->" << e.to << ":" << e.cost << "\n"; }
        }
        return (os << "]\n");
    }
    const std::size_t V;
    std::vector<std::vector<Edge>> edge, rev_edge;
};
//!============================================!//
//!    8888ba.88ba             oo              !//
//!    88  '8b  '8b                            !//
//!    88   88   88  .d8888b.  dP  88d888b.    !//
//!    88   88   88  88'  '88  88  88'  '88    !//
//!    88   88   88  88.  .88  88  88    88    !//
//!    dP   dP   dP  '88888P8  dP  dP    dP    !//
//!============================================!//
int main()
{
    int N, M;
    std::cin >> N >> M;
    CostGraph<int> G(N);
    for (int i = 0, a, b, c; i < M; i++) { std::cin >> a >> b >> c, a--, b--, G.addEdge(a, b, c, true); }
    using T = int;
    auto Dijkstra = [&](const CostGraph<T>& g, const int s, const int c) {
        using P = std::pair<int, int>;
        std::map<P, int> d;
        using PP = std::pair<T, P>;
        std::priority_queue<PP, std::vector<PP>, std::greater<PP>> q;
        d[{s, c}] = 0, q.push({0, {s, c}});
        while (not q.empty()) {
            const T cost = q.top().first;
            const int v = q.top().second.first;
            const int c = q.top().second.second;
            q.pop();
            if (d.find({v, c}) != d.end() and d[{v, c}] < cost) { continue; }
            for (const auto& e : g.edge[v]) {
                if (c == 0 or e.cost == c) {
                    if (d.find({e.to, e.cost}) != d.end() and d[{e.to, e.cost}] <= cost) { continue; }
                    d[{e.to, e.cost}] = cost, q.push({cost, {e.to, e.cost}});
                } else {
                    if (d.find({e.to, e.cost}) != d.end() and d[{e.to, e.cost}] <= cost + 1) { continue; }
                    d[{e.to, e.cost}] = cost + 1, q.push({cost + 1, {e.to, e.cost}});
                }
            }
        }
        return d;
    };
    const auto D = Dijkstra(G, 0, 0);
    int ans = INF<int>;
    for (int i = 0; i <= 100000; i++) {
        if (D.find({N - 1, i}) != D.end()) { chmin(ans, D.at({N - 1, i})); }
    }
    std::cout << (ans == INF<int> ? -1 : (ans + 1) * K) << std::endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:154:54: error: 'K' was not declared in this scope
  154 |     std::cout << (ans == INF<int> ? -1 : (ans + 1) * K) << std::endl;
      |                                                      ^