1724.cpp

#include <bits/stdc++.h>

using namespace std;

#define print_op(...) ostream& operator<<(ostream& out, const __VA_ARGS__& u)
template<typename A, typename B> print_op(pair<A, B>) { return out << "(" << u.first << ", " << u.second << ")"; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> print_op(T_container) { out << "{"; string sep; for (const T &x : u) out << sep << x, sep = ", "; return out << "}"; }
template<typename T> void dbg_out(string s, T x) {cerr << "\033[1;35m" << s << "\033[0;32m = \033[33m" << x << "\033[0m\n";}
template<typename T, typename... Args> void dbg_out(string s, T x, Args... args) {for (int i=0, b=0; i<(int)s.size(); i++) if (s[i] == '(' || s[i] == '{') b++; else
if (s[i] == ')' || s[i] == '}') b--; else if (s[i] == ',' && b == 0) {cerr << "\033[1;35m" << s.substr(0, i) << "\033[0;32m = \033[33m" << x << "\033[31m | "; dbg_out(s.substr(s.find_first_not_of(' ', i + 1)), args...); break;}}
#ifdef LOCAL
#define dbg(...) dbg_out(#__VA_ARGS__, __VA_ARGS__)
#else
#define dbg(...)
#endif

#define ar array
#define ll long long
#define ld long double
#define sz(x) ((int)x.size())
#define rep(i, a, b) for (int i = (int)(a); i < (int)(b); i++) 
#define all(a) (a).begin(), (a).end()

const int MAX_N = 1e5 + 5;
const int MAX_L = 20;
const int MAX_C = 26;
const ll MOD = 1e9 + 7;
const ll INF = 1e9;
const ld EPS = 1e-9;

template<typename T> struct Matrix {
    int n, m;
    vector<vector<T>> mat;
    Matrix(int _n, int _m) : n(_n), m(_m), mat(n, vector<T>(m, 2e18)) {}
    Matrix(int _n) : Matrix(_n, _n) { for (int i = 0; i < n; i++) mat[i][i] = 0; } // identity matrix
    Matrix(const vector<vector<T>> &_mat) : n((int) _mat.size()), m((int) _mat[0].size()), mat(_mat) {}
    Matrix operator * (const Matrix &other) const {
        Matrix ret(n, other.m);
        for (int i = 0; i < n; i++)
            for (int k = 0; k < m; k++)
                for (int j = 0; j < other.m; j++)
                    ret.mat[i][j] = min(ret.mat[i][j], mat[i][k] + other.mat[k][j]);
        return ret;
    }
    friend Matrix operator + (Matrix a, const Matrix &b) { return a += b; }
    friend Matrix operator - (Matrix a, const Matrix &b) { return a -= b; }
    Matrix& operator *= (const Matrix &other) { return *this = *this * other; }
    vector<T>& operator [] (int i) { return mat[i]; }
    friend Matrix power(Matrix a, long long b) {
        Matrix ret(a.n);
        while (b > 0) {
            if (b & 1) ret *= a;
            a *= a;
            b >>= 1;
        }
        return ret;
    }
    friend ostream& operator << (ostream &os, const Matrix &a) { return os << a.mat; }
    void print() {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) cout << mat[i][j] << " ";
            cout << "\n";
        }
    }
};
 
void solve(int tc = 0) {
    int n, m, k; cin >> n >> m >> k;
    Matrix<ll> A(n), B(n, n);
    while (m--) {
        int u, v; ll w; cin >> u >> v >> w; u--; v--;
        B.mat[u][v] = min(B.mat[u][v], w);
    }
    A = A * power(B, k);
    cout << (A.mat[0][n - 1] == 2e18 ? -1 : A.mat[0][n - 1]) << "\n";
}

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL);
    int tc = 1;
    // cin >> tc;
    for (int t = 1; t <= tc; t++) {
        // cout << "Case #" << t << ": ";
        solve(t);
    }
}