#include <bits/stdc++.h>
#include "cyberland.h"
#define i64 long long
#define ff first
#define ss second
using namespace std;
double solve(int n, int m, int K, int H, vector<int> x, vector<int> y, vector<int> c, vector<int> arr) {
vector<vector<int>> G(n);
for (int i = 0; i < m; ++i) {
G[x[i]].emplace_back(i);
G[y[i]].emplace_back(i);
}
// cout << n << " " << m << endl;
vector<vector<double>> dis(n, vector<double>(K, 1e18));
priority_queue<pair<double, pair<int, int>>, vector<pair<double, pair<int, int>>>, greater<pair<double, pair<int, int>>>> pq;
dis[0][0] = 0;
pq.emplace(0, pair(0, 0));
while (not pq.empty()) {
auto w = pq.top().ff;
auto v = pq.top().ss.ff;
auto used = pq.top().ss.ss;
pq.pop();
// cout << w << " " << v << " " << used << endl;
if (w != dis[v][used]) continue;
double nw;
for (int eidx : G[v]) {
int u = x[eidx] ^ y[eidx] ^ v;
if (arr[u] == 0) {
nw = 0;
if (dis[u][used] > nw) {
dis[u][used] = nw;
pq.emplace(nw, pair(u, used));
}
}
if (arr[u] == 2 and used < K) {
nw = (w + c[eidx]) / 2;
if (dis[u][used + 1] > nw) {
dis[u][used + 1] = nw;
pq.emplace(nw, pair(u, used + 1));
}
}
nw = w + c[eidx];
if (dis[u][used] > nw) {
dis[u][used] = nw;
pq.emplace(nw, pair(u, used));
}
}
}
double res = 1e18;
for (int i = 0; i <= K; ++i) res = min(res, dis[H][i]);
return (res == 1e18 ? -1 : res);
}
// int main() {
// int T;
// assert(1 == scanf("%d", &T));
// while (T--){
// int N,M,K,H;
// assert(4 == scanf("%d %d %d\n%d", &N, &M, &K, &H));
// std::vector<int> x(M);
// std::vector<int> y(M);
// std::vector<int> c(M);
// std::vector<int> arr(N);
// for (int i = 0; i < N; i++) assert(1 == scanf("%d", &arr[i]));
// for (int i = 0; i < M; i++) assert(3 == scanf("%d %d %d", &x[i], &y[i], &c[i]));
// printf("%.12lf\n", solve(N, M, K, H, x, y, c, arr));
// }
// }
