#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

struct vertex {
    int num;
    int weight;
};


#define int long long
void FordBellman() {
    int N, m, b, k, s, f;
    vertex a;
    cin >> N >> m >> k >> s >> f;
    vector<vector<vertex>> g(N);
    for (int i = 0; i < m; ++i) {
        cin >> b >> a.num >> a.weight;
        a.num--;
        g[b - 1].push_back(a);
    }
    vector<int> d(N, 10e12);
    d[s - 1] = 0;
    for (int i = 0; i < k; ++i) {
        auto d_new = d;
        for (int j = 0; j < N; ++j) {
            for (auto [to, w] : g[j]) {
                if (d[j] != 10e12)
                    d_new[to] = min(d[to], d[j] + w);
            }
        }
        d = d_new;

    }
    std::cout << d[f - 1];
}
int32_t main() {
    FordBellman();
    return 0;
}