#include <bits/stdc++.h>
#define FASTIO
using namespace std;

using ll = long long;
using Vi = std::vector<int>;
using Vl = std::vector<ll>;
using Pii = std::pair<int, int>;
using Pll = std::pair<ll, ll>;

constexpr int I_INF = std::numeric_limits<int>::max();
constexpr ll L_INF = std::numeric_limits<ll>::max();

template <typename T1, typename T2>
inline bool chmin(T1& a, const T2& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T1, typename T2>
inline bool chmax(T1& a, const T2& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <std::ostream& os = std::cout>
class Prints {
private:
    class __Prints {
    public:
        __Prints(const char* sep, const char* term) : sep(sep), term(term) {}
        template <class... Args>
#if __cplusplus >= 201703L
        auto operator()(const Args&... args) const -> decltype((os << ... << std::declval<Args>()), void()) {
#else
        void operator()(const Args&... args) const {
#endif
            print(args...);
        }
        template <typename T>
#if __cplusplus >= 201703L
        auto pvec(const T& vec, size_t sz) const -> decltype(os << std::declval<decltype(std::declval<T>()[0])>(), void()) {
#else
        void pvec(const T& vec, size_t sz) const {
#endif
            for (size_t i = 0; i < sz; i++)
                os << vec[i] << (i == sz - 1 ? term : sep);
        }
        template <typename T>
#if __cplusplus >= 201703L
        auto pmat(const T& mat, size_t h, size_t w) const -> decltype(os << std::declval<decltype(std::declval<T>()[0][0])>(), void()) {
#else
        void pmat(const T& mat, size_t h, size_t w) const {
#endif
            for (size_t i = 0; i < h; i++)
                for (size_t j = 0; j < w; j++)
                    os << mat[i][j] << (j == w - 1 ? term : sep);
        }

    private:
        const char *sep, *term;
        void print() const { os << term; }
        void print_rest() const { os << term; }
        template <class T, class... Tail>
        void print(const T& head, const Tail&... tail) const { os << head, print_rest(tail...); }
        template <class T, class... Tail>
        void print_rest(const T& head, const Tail&... tail) const { os << sep << head, print_rest(tail...); }
    };

public:
    Prints() {}
    __Prints operator()(const char* sep = " ", const char* term = "\n") const { return __Prints(sep, term); }
};

Prints<> prints;
Prints<std::cerr> prints_err;

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

template <typename T>
struct WeightedEdge {
    int to;
    T cost;
    constexpr WeightedEdge(int to, T cost = -1) noexcept : to(to), cost(cost) {}
};
template <typename T>
using WeightedGraph = std::vector<std::vector<WeightedEdge<T>>>;

void solve() {
    ll N, S, T, K;
    cin >> N >> S >> T >> K;
    --S, --T;
    Vl X(N);
    for (ll i = 0; i < N; i++) {
        cin >> X[i];
    }
    ll M;
    cin >> M;
    WeightedGraph<ll> g(N);
    for (ll i = 0; i < M; i++) {
        ll a, b, y;
        cin >> a >> b >> y;
        --a, --b;
        g[a].emplace_back(b, X[b] + y);
    }
    vector dp(N, Vl(K + 1, L_INF));
    vector pre(N, vector(K + 1, Pll{-1, -1}));
    using Tup = tuple<ll, ll, ll>;
    priority_queue<Tup, vector<Tup>, greater<Tup>> pq;
    dp[S][1] = X[S];
    pq.emplace(X[S], S, 1);
    while (!pq.empty()) {
        auto [cost, u, k] = pq.top();
        pq.pop();
        if (dp[u][k] < cost) continue;
        for (auto [to, c] : g[u]) {
            ll nc = cost + c;
            ll nk = min(k + 1, K);
            if (dp[to][nk] > nc) {
                dp[to][nk] = nc;
                pre[to][nk] = {u, k};
                pq.emplace(nc, to, nk);
            }
        }
    }
    if (dp[T][K] == L_INF) {
        prints()("Impossible");
        return;
    }
    Vl path;
    {
        ll u_cur = T, k_cur = K;
        while (u_cur != -1) {
            path.emplace_back(u_cur);
            tie(u_cur, k_cur) = pre[u_cur][k_cur];
        }
    }
    reverse(path.begin(), path.end());
    prints()("Possible");
    prints()(dp[T][K]);
    prints()(path.size());
    for (auto u : path) {
        cout << u + 1 << " ";
    }
    prints()();
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

int main() {
#ifdef FASTIO
    std::cin.tie(nullptr), std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);
#endif
#ifdef FILEINPUT
    std::ifstream ifs("./in_out/input.txt");
    std::cin.rdbuf(ifs.rdbuf());
#endif
#ifdef FILEOUTPUT
    std::ofstream ofs("./in_out/output.txt");
    std::cout.rdbuf(ofs.rdbuf());
#endif
    std::cout << std::setprecision(18) << std::fixed;
    solve();
    std::cout << std::flush;
    return 0;
}