#include <bits/stdc++.h>
using namespace std;
#ifdef MIKU
string dbmc = "\033[1;38;2;57;197;187m", dbrs = "\033[0m";
#define debug(x...) cout << dbmc << "[" << #x << "]: ", dout(x)
void dout() { cout << dbrs << endl; }
template <typename T, typename ...U>
void dout(T t, U ...u) { cout << t << (sizeof...(u) ? ", " : ""); dout(u...); }
#else
#define debug(...) 39
#endif
// #define int long long
#define fs first
#define sc second
#define mp make_pair
#define FOR(i, j, k) for (int i = j, Z = k; i < Z; i++)
typedef pair<int, int> pii;
typedef pair<double, int> pdi;
using ll = __int128_t;
namespace {
const int MXN = 100005, MXK = 35;
int n, m, k, h;
vector<int> u, v, w, a;
vector<pdi> edge[MXN * MXK];
double dis[MXN * MXK];
vector<int> zero;
bitset<MXN> b;
inline int f(int x, int y) {
return x * n + y;
}
void build_graph1() {
FOR(i, 0, m) {
int x = u[i], y = v[i];
double z = w[i];
if (x != h) edge[x].push_back(mp(z, y));
if (y != h) edge[y].push_back(mp(z, x));
}
}
void DFS(int id) {
b[id] = true;
for (auto &[w, i] : edge[id]) {
if (b[i]) continue;
DFS(i);
}
}
void find_zero() {
zero.clear();
zero.push_back(1);
FOR(i, 1, n + 1) b[i] = 0;
DFS(1);
FOR(i, 1, n + 1) if (a[i] == 0 && b[i]) zero.push_back(i);
}
void cls_graph() {
FOR(i, 1, n + 1) edge[i].clear();
}
void build_graph2() {
auto PUT = [&](int x, int y, double z) -> void {
if (a[x] == 2) {
FOR(i, 0, k) edge[f(i, x)].push_back(mp(z * (2LL << i), f(i + 1, y)));;
}
FOR(i, 0, k + 1) edge[f(i, x)].push_back(mp(z * (1LL << i), f(i, y)));
};
for (auto &i : zero) edge[0].push_back(mp(0.0, i));
FOR(i, 0, m) {
int x = u[i], y = v[i];
double z = w[i];
if (x != h) PUT(x, y, z);
if (y != h) PUT(y, x, z);
}
}
void DIJKSTRA() {
priority_queue<pdi, vector<pdi>, greater<pdi>> pq;
fill(dis, dis + n * k + n + 1, 3.9e239);
pq.push(mp(0.0, 0));
while (pq.size()) {
auto [len, id] = pq.top();
pq.pop();
if (dis[id] < 3.9e239) continue;
dis[id] = len;
for (auto &[w, i] : edge[id]) {
if (dis[i] < 3.9e239) continue;
pq.push(mp(len + w, i));
}
}
}
void RESET() {
FOR(i, 0, n * (k + 1) + 1) edge[i].clear();
}
double APIO() {
assert(k <= 30);
build_graph1();
find_zero();
cls_graph();
build_graph2();
DIJKSTRA();
double ans = 3.9e239;
FOR(i, 0, k + 1) {
ans = min(ans, dis[f(i, h)] / (1LL << i));
}
RESET();
return (ans >= 2e18 ? -1.0 : ans);
}
}
double solve(int N, int M, int K, int H, vector<int> U, vector<int> V, vector<int> W, vector<int> A) {
H++;
for (auto &i : U) i++;
for (auto &i : V) i++;
A.insert(A.begin(), 0);
::n = N;
::m = M;
::k = K;
::h = H;
::u = U;
::v = V;
::w = W;
::a = A;
return APIO();
}
#ifdef MIKU
void READ(vector<int> &v) {
int n;
cin >> n;
v.resize(n);
for (auto &i : v) cin >> i;
}
void miku() {
int n, m, k, h;
vector<int> u, v, w, a;
cin >> n >> m >> k >> h;
READ(u);
READ(v);
READ(w);
READ(a);
cout << solve(n, m, k, h, u, v, w, a) << '\n';
}
int32_t main() {
cin.tie(0) -> sync_with_stdio(false);
cin.exceptions(cin.failbit);
miku();
return 0;
}
#endif
