#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N, S, T, K;
	cin >> N >> S >> T >> K; --S; --T;
	vector<int> X(N);
	REP(i, N) scanf("%d", &X[i]);
	int M;
	cin >> M;
	vector<vector<pii>> g(N);
	REP(i, M) {
		int a, b, y;
		scanf("%d %d %d", &a, &b, &y);
		--a; --b;
		g[a].emplace_back(b, y + X[a]);
	}
	
	vector dist(N, vector<ll>(K, longINF));
	vector prv(N, vector<pii>(K, {-1, -1}));
	// r 回 (chmin(r, K - 1)) dist, vertex
	using tup = tuple<int, ll, int>;
	priority_queue<tup, vector<tup>, greater<tup>> pq;
	dist[S][0] = 0;
	pq.emplace(0, 0, S);
	while (!pq.empty()) {
		auto [k, d, u] = pq.top(); pq.pop();
		if (dist[u][k] != d) continue;
		for (auto [v, l] : g[u]) {
			const int nk = min(k + 1, K - 1);
			const ll nd = d + l;
			if (chmin(dist[v][nk], nd)) {
				prv[v][nk] = {u, k};
				pq.emplace(nk, nd, v);
			}
		}
	}
	if (dist[T][K - 1] == longINF) puts("Impossible");
	else {
		puts("Possible");
		cout << dist[T][K - 1] + X[T] << endl;
		
		int u = T, k = K - 1;
		vector<int> ans;
		while (u != -1) {
			ans.emplace_back(u);
			auto [nu, nk] = prv[u][k];
			u = nu; k = nk;
		}
		reverse(ALL(ans));
		cout << ans.size() << endl;
		REP(i, ans.size()) printf("%d%c", ans[i] + 1, " \n"[i + 1 == ans.size()]);
	}
}