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

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

template <typename T>
using pqueue = priority_queue<T, vector<T>, greater<T>>;

int main() {
    constexpr int64_t inf = INT64_MAX / 4;
    constexpr auto inv = make_tuple(-1, -1);

    int n, s, t, k;
    cin >> n >> s >> t >> k;
    --s; --t;

    auto x = vec<int>(uns, n);
    for (auto &e : x) cin >> e;

    int m; cin >> m;

    auto g = vec<tuple<int, int>>(uns, n, 0);
    for (int i = 0; i < m; ++i) {
        int a, b, y; cin >> a >> b >> y; --a; --b;
        g[a].push_back({ b, x[b] + y });
    }

    pqueue<tuple<int64_t, int, int>> que;
    auto dist = vec<int64_t>(inf, n, k + 1);
    auto prev = vec<tuple<int, int>>(inv, n, k + 1);

    que.push({ x[s], s, 1 });
    dist[s][1] = x[s];
    while (!empty(que)) {
        auto [d, v, c] = que.top(); que.pop();

        if (dist[v][c] < d) {
            continue;
        }

        for (auto [u, w] : g[v]) {
            if (dist[u][min(k, c + 1)] <= d + w) {
                continue;
            }

            dist[u][min(k, c + 1)] = d + w;
            prev[u][min(k, c + 1)] = { v, c };
            que.push({ dist[u][min(k, c + 1)], u, min(k, c + 1) });
        }
    }

    if (dist[t][k] == inf) {
        cout << "Impossible" << endl;
        return 0;
    }

    auto path = [&] {
        auto path = vec<int>(uns, 0);

        int v = t, c = k;
        while (0 <= v && 0 <= c) {
            path.push_back(v);

            auto [pv, pc] = prev[v][c];
            v = pv; c = pc;
        }

        reverse(begin(path), end(path));
        return path;
    }();

    cout << "Possible" << endl;
    cout << dist[t][k] << endl;

    cout << size(path) << endl;
    cout << path[0] + 1;
    for (int i = 1; i < size(path); ++i) {
        cout << ' ' << path[i] + 1;
    }
    cout << endl;
}