#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define each(e, v) for(auto &e: v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

struct io_setup{
    io_setup(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

vector<ll> a;
int N, K;

template<typename T, bool directed = false>
struct Weighted_Graph{
    struct edge{
        int to; T cost; int id;
        edge(int to, T cost, int id) : to(to), cost(cost), id(id) {}
    };

    vector<vector<edge>> es;
    const T INF_T;
    const int n;
    int m;

    vector<T> d;
    vector<int> pre_v;

    Weighted_Graph(int n) : es(n), INF_T(numeric_limits<T>::max()/2), n(n), m(0), d(n), pre_v(n) {}

    void add_edge(int from, int to, T cost){
        es[from].emplace_back(to, cost, m);
        if(!directed) es[to].emplace_back(from, cost, m);
        m++;
    }

    T dijkstra(int s, int t = 0){
        fill(begin(d), end(d), INF_T);
        using P = pair<T, int>;
        priority_queue<P, vector<P>, greater<P> > que;
        que.emplace(d[s] = 0, s);
        while(!que.empty()){
            auto [p, i] = que.top(); que.pop();
            if(p > d[i]) continue;
            for(auto &e: es[i]){
                if(d[i]+e.cost < d[e.to]){
                    pre_v[e.to] = i, que.emplace(d[e.to] = d[i]+e.cost, e.to);
                }
            }
        }
        return d[t];
    }

    vector<int> shortest_path(int s, int t){
        //if(dijkstra(s, t) == INF_T) return {};
        vector<int> ret;
        for(int now = t; now != s; now = pre_v[now]) ret.push_back(now);
        ret.push_back(s), reverse(begin(ret), end(ret));
        return ret;
    }
};

int main(){
    int S, T; cin >> N >> S >> T >> K; S--, T--;

    Weighted_Graph<ll, true> G(N*K);

    a.resize(N);
    rep(i, N) cin >> a[i];

    int M; cin >> M;

    rep(i, M){
        int u, v; ll c; cin >> u >> v >> c; u--, v--;
        c += a[v];
        rep(j, K-1){
            G.add_edge(u*K+j, v*K+j+1, c);
        }
        G.add_edge(u*K+K-1, v*K+K-1, c);
    }

    ll ans = G.dijkstra(S*K, T*K+K-1);

    if(ans >= INF) {cout << "Impossible\n"; return 0;}

    //rep(i, N*K) cout << G.d[i] << ' '; cout << '\n';

    cout << "Possible\n" << ans+a[S] << '\n';
    vector<int> path = G.shortest_path(S*K, T*K+K-1);
    int n = sz(path);
    cout << n << '\n';
    rep(i, n) cout << (path[i]/K)+1 << (i == n-1? '\n' : ' ');
}