#include "cyberland.h"
#include <bits/stdc++.h>
using namespace std;
const long long inf=1e18;
bool u[100005]; vector <pair<int,double> > v[100005];
vector <int> pt; int h;
void dfs(int i){
u[i]=1; if (i==h) return;
for (auto j:v[i]){
if (!u[j.first]) dfs(j.first);
}
}
double solve(int N, int M, int K, int H, vector<int> x, vector<int> y, vector<int> c, vector<int> arr) {
for (int i=0; i<N; i++) v[i].clear(); h=H;
for (int i=0; i<M; i++){
v[x[i]].push_back({y[i],c[i]});
v[y[i]].push_back({x[i],c[i]});
}
arr[0]=0; set <tuple<double, int, int> > s;
double d[N][K+1];
for (int i=0; i<N; i++){
for (int j=0; j<=K; j++) d[i][j]=inf;
} d[0][0]=0;
/*for (int i=0; i<N; i++) u[i]=0;
dfs(0);
for (int i=0; i<N; i++){
if (arr[i]==0 && u[i]){
s.insert({0,i,0}); d[i][0]=0;
}
}*/ s.insert(make_tuple(0,0,0));
while (!s.empty()){
int X=get<1>(*s.begin()),Y=get<2>(*s.begin()); s.erase(s.begin());
for (auto i:v[X]){
double w=d[X][Y]+i.second;
if (d[i.first][Y]>w){
s.erase(make_tuple(d[i.first][Y],i.first,Y));
d[i.first][Y]=w;
s.insert(make_tuple(d[i.first][Y],i.first,Y));
}
if (arr[i.first]==0 && d[i.first][Y]>0){
s.erase(make_tuple(d[i.first][Y],i.first,Y));
d[i.first][Y]=0;
s.insert(make_tuple(0,i.first,Y));
}
}
for (auto i:v[X]){
if (arr[i.first]!=2) continue;
if (Y+1<=K){
double w=(d[X][Y]+i.second)/2.0;
if (d[i.first][Y+1]>w){
s.erase(make_tuple(d[i.first][Y+1],i.first,Y+1));
d[i.first][Y+1]=w;
s.insert(make_tuple(d[i.first][Y+1],i.first,Y+1));
}
}
}
}
//for (int i=0; i<N; i++) cout<<i<<" -> "<<d[i]<<"\n";
double mn=inf;
for (int i=0; i<=K; i++) mn=min(mn,d[H][i]);
if (mn==inf) return -1;
return mn;
}
