#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<long long,pair<int,int>>
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; }
int n, s, t, k;
struct Edge {
	int to, cost;
	Edge(int _to, int _cost) :to(_to), cost(_cost) {}
};
vector<Edge>g[200005]; vector<vector<int>> data(3, vector<int>(4));
vector<long long>x;
void dikstra() {
	vector<vector<long long>> d(n, vector<long long>(k, LINF));
	vector<vector<pair<int, int>>> pre(n, vector<pair<int, int>>(k, { -1,-1 }));
	priority_queue<P, vector<P>, greater<P> > q;//小さいもの順
	q.push({ x[s], { s,0 } });
	d[s][0] = x[s];
	while (!q.empty()) {
		auto tmp = q.top();
		q.pop();
		long long cost = tmp.first;
		int pos = tmp.second.first;
		int count = tmp.second.second;
		if (cost > d[pos][count]) continue;
		for (Edge e : g[pos]) {
			long long ncost = cost + e.cost + x[e.to];
			int npos = e.to;
			int ncount = min(k - 1, count + 1);
			if (ncost < d[npos][ncount]) {
				pre[npos][ncount] = { pos,count };
				d[npos][ncount] = ncost;
				q.push({ d[npos][ncount], {npos,ncount} });
			}
		}
	}
	if (LINF == d[t][k - 1]) {
		cout << "Impossible" << endl;
	}
	else {
		cout << "Possible" << endl;
		cout << d[t][k - 1] << endl;
		vector<int>ans;
		ans.push_back(t);
		pair<int, int>p = pre[t][k - 1];
		while (true) {
			ans.push_back(p.first);
			p = pre[p.first][p.second];
			if (p.first == -1)break;
		}
		cout << ans.size() << endl;
		rrep(i, ans.size()) {
			cout << ans[i] + 1 << " ";
		}
	}
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin >> n >> s >> t >> k;
	s--; t--;
	x.resize(n);
	rep(i, n)cin >> x[i];
	int m; cin >> m;
	rep(i, m) {
		int a, b, y; cin >> a >> b >> y;
		a--; b--;
		g[a].emplace_back(b, y);
	}
	dikstra();
	return 0;
}