/*
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
//*/

#include <bits/stdc++.h>

// #include <atcoder/all>

using namespace std;
// using namespace atcoder;

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define DEBUG_VEC(v)                                        \
    cerr << #v << ":";                                      \
    for (int iiiiiiii = 0; iiiiiiii < v.size(); iiiiiiii++) \
        cerr << " " << v[iiiiiiii];                         \
    cerr << endl;
#define DEBUG_MAT(v)                            \
    cerr << #v << endl;                         \
    for (int i = 0; i < v.size(); i++) {        \
        for (int j = 0; j < v[i].size(); j++) { \
            cerr << v[i][j] << " ";             \
        }                                       \
        cerr << endl;                           \
    }
typedef long long ll;
#define int ll

#define vi vector<int>
#define vl vector<ll>
#define vii vector<vector<int>>
#define vll vector<vector<ll>>
#define vs vector<string>
#define pii pair<int, int>
#define pis pair<int, string>
#define psi pair<string, int>
#define pll pair<ll, ll>
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
    return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template <class S, class T>
ostream &operator<<(ostream &os, pair<S, T> p) {
    os << "(" << p.first << ", " << p.second << ")";
    return os;
}
#define X first
#define Y second
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define rrep1(i, n) for (int i = (int)(n); i > 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(), c.end()
void YES(bool t = true) {
    cout << (t ? "YES" : "NO") << endl;
}
void Yes(bool t = true) { cout << (t ? "Yes" : "No") << endl; }
void yes(bool t = true) { cout << (t ? "yes" : "no") << endl; }
void NO(bool t = true) { cout << (t ? "NO" : "YES") << endl; }
void No(bool t = true) { cout << (t ? "No" : "Yes") << endl; }
void no(bool t = true) { cout << (t ? "no" : "yes") << endl; }
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const long double pi = 3.1415926535897932384626433832795028841971L;
int popcount(ll t) { return __builtin_popcountll(t); }
// int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
// int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
vi dx = {0, 1, 0, -1}, dy = {-1, 0, 1, 0};
// vi dx2 = { 1,1,0,-1,-1,-1,0,1 }, dy2 = { 0,1,1,1,0,-1,-1,-1 };
struct Setup_io {
    Setup_io() {
        ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
        cout << fixed << setprecision(25);
    }
} setup_io;
// const ll MOD = 1000000007;
const ll MOD = 998244353;
// #define mp make_pair
//#define endl '\n'

signed main() {
    int n, s, t, k;
    cin >> n >> s >> t >> k;
    s--;
    t--;
    vi x(n);
    rep(i, n) cin >> x[i];

    int m;
    cin >> m;
    vector<vector<pll>> G(n);
    rep(i, m) {
        int u, v, y;
        cin >> u >> v >> y;
        u--;
        v--;
        G[u].emplace_back(v, y);
    }

    vll dp(n, vl(k + 1, INF));
    vector<vector<pii>> pre(n, vector<pii>(k));
    dp[s][0] = x[s];
    pre[s][0] = pii(-1, -1);
    using P = pair<ll, pii>;
    priority_queue<P, vector<P>, greater<P>> pq;

    pq.push(P(x[s], pii(s, 0)));
    while (pq.size()) {
        auto [cost, uk] = pq.top();
        pq.pop();
        auto [u, i] = uk;

        if (dp[u][i] < cost) continue;
        int ni = min(i + 1, k - 1);
        for (auto [j, y] : G[u]) {
            ll ncost = cost + y + x[j];
            if (chmin(dp[j][ni], ncost)) {
                pq.push(P(ncost, pii(j, ni)));
                pre[j][ni] = pii(u, i);
            }
        }
    }

    if (dp[t][k - 1] == INF) {
        cout << "Impossible" << endl;
        return 0;
    }

    cout << "Possible" << endl;
    cout << dp[t][k - 1] << endl;
    vector<pii> his;
    his.push_back(pii(t, k - 1));
    while (true) {
        auto [i, j] = his.back();
        his.push_back(pre[i][j]);
        if (his.back().first == -1) break;
    }
    his.pop_back();
    reverse(all(his));
    cout << his.size() << endl;
    rep(i, his.size()) {
        cout << his[i].first + 1 << " ";
    }
    cout << endl;
}