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

struct node {
	int u, dis;

	node(int u, int dis) {
		this->u = u;
		this->dis = dis;
	}

	bool operator<(const node& a)const {
		return dis > a.dis;
	}
};

struct vertex {
	int v, w;

	vertex(int v, int w) {
		this->v = v;
		this->w = w;
	}
};

const long long MAXSIZE(10010), INF(0x7FFFFFFFFFFFFFFF);
vector<vertex> vec[MAXSIZE * 15];
priority_queue<node> q;
long long dis[MAXSIZE * 15], N, M, K;
bool flag[MAXSIZE * 15];

void init() {
	for (int i = 0; i < MAXSIZE * 15; i++) {
		flag[i] = false;
		dis[i] = INF;
	}
}

void buildEdge(int u, int v, int w) {
	for (int i = 0; i < K; i++) {
		vec[u].push_back(vertex(v + N * (1 + i), 0));
		vec[v].push_back(vertex(u + N * (1 + i), 0));
		vec[u + N * (1 + i)].push_back(vertex(v + N * (1 + i), w));
		vec[v + N * (1 + i)].push_back(vertex(u + N * (1 + i), w));
	}
}

void dijkstra(int u) {
	q.push(node(u, 0));
	dis[u] = 0;

	while (!q.empty()) {
		node n = q.top();
		q.pop();

		if (flag[n.u]) continue;
		flag[n.u] = true;

		for (int i = 0; i < vec[n.u].size(); i++) {
			vertex v = vec[n.u][i];
			if (n.dis + v.w <= dis[v.v]) {
				dis[v.v] = n.dis + v.w;
				q.push(node(v.v, n.dis + v.w));
			}
		}
	}
}

int main() {
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	long long s, t, u, v, w, answer(INF);
	cin >> N >> M >> K;
	cin >> s >> t;
	init();

	while (M--) {
		cin >> u >> v >> w;
		vec[u].push_back(vertex(v, w));
		vec[v].push_back(vertex(u, w));
		buildEdge(u, v, w);
	}

	dijkstra(s);

	for (int i = 0; i <= K; i++) {
		answer = min(answer, dis[t + N * i]);
	}

	cout << answer;

	return 0;
}