#pragma GCC diagnostic warning "-std=c++11"
#include <bits/stdc++.h>
#include "cyberland.h"
#define pb push_back
#define f first
#define s second
#define MOD 1000000007
#define flush fflush(stdout)
#define all(x) (x).begin(),(x).end()
#define allr(x) (x).rbegin(), (x).rend()
#define pii pair<int,int>
using namespace std;
const int N=1e5+5;
long long n,m,T,k,h,dist[N],fix[N],cr[N],st,big=1e18;
vector<pii> g[N];
double solve(int N, int M, int K, int H, vector<int> x, vector<int> y, vector<int> c, vector<int> arr) {
arr[0]=0; n=N; m=M; k=K; h=H;
for (int i=0; i<m; i++) {
g[x[i]].pb({y[i],c[i]});
g[y[i]].pb({x[i],c[i]});
}
st=0;
for (int i=0; i<n; i++) dist[i]=1e18;
for (int i=0; i<n; i++) fix[i]=0;
dist[st]=0;
// dif
fix[h]=1;
// dif
priority_queue<pii> q; q.push({0,st});
while (!q.empty()) {
int v=q.top().s; q.pop();
if (fix[v]) continue;
fix[v]=1;
for (auto X:g[v]) {
int u=X.f,w=X.s;
if (dist[u]>dist[v]+w) {
dist[u]=dist[v]+w;
q.push({-dist[u],u});
}
}
}
for (int i=0; i<n; i++) {
if (dist[i]<big) cr[i]=1;
}
st=h;
for (int i=0; i<n; i++) dist[i]=1e18;
for (int i=0; i<n; i++) fix[i]=0;
dist[st]=0;
q.push({0,st});
while (!q.empty()) {
int v=q.top().s; q.pop();
if (fix[v]) continue;
fix[v]=1;
for (auto X:g[v]) {
int u=X.f,w=X.s;
if (dist[u]>dist[v]+w) {
dist[u]=dist[v]+w;
q.push({-dist[u],u});
}
}
}
long long ans=big;
for (int i=0; i<n; i++) {
if (cr[i] && arr[i]==0) ans=min(ans,dist[i]);
}
double anss=ans;
if (ans==big) anss=-1;
return anss;
}
