#include "cyberland.h"
#include <vector>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define F first
#define S second
#define pb push_back
#define sz(a) (int)a.size()
#define all(x) (x).begin(), (x).end()
vector<vector<ld>> dist;
vector<vector<pair<int, int>>> adj;
vector<int> a;
const ld inf = 1e15+9;
ld ans=inf;
void go(int nw, int h, int remain, ld curr){
if(dist[nw][remain]<=curr) return;
dist[nw][remain]=curr;
if(nw==h) return;
for(auto& u : adj[nw]){
ld nw_curr=curr;
if(a[nw]==0) nw_curr=0;
go(u.F, h, remain, nw_curr+u.S);
if(a[nw]==2 && remain>0){
nw_curr/=2.0;
go(u.F, h, remain-1, nw_curr+u.S);
}
}
}
double solve(int N, int M, int K, int H, vector<int> x, vector<int> y, vector<int> c, vector<int> arr) {
a=arr;
dist.assign(N, vector<ld>(K+1, inf));
adj.resize(N);
for(int i=0; i<M; i++){
adj[x[i]].pb({y[i], c[i]});
adj[y[i]].pb({x[i], c[i]});
}
go(0, H, K, 0);
for(int i=0; i<=K; i++) ans=min(ans, dist[H][i]);
if(ans==inf) return -1;
return ans;
}
