import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.PriorityQueue;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		int s = Integer.parseInt(sa[1]) - 1;
		int t = Integer.parseInt(sa[2]) - 1;
		int k = Integer.parseInt(sa[3]);
		sa = br.readLine().split(" ");
		int[] x = new int[n];
		for (int i = 0; i < n; i++) {
			x[i] = Integer.parseInt(sa[i]);
		}
		List<List<Hen>> list = new ArrayList<>(n);
		for (int i = 0; i < n; i++) {
			list.add(new ArrayList<>());
		}
		int m = Integer.parseInt(br.readLine());
		for (int i = 0; i < m; i++) {
			sa = br.readLine().split(" ");
			int a = Integer.parseInt(sa[0]) - 1;
			int b = Integer.parseInt(sa[1]) - 1;
			int c = Integer.parseInt(sa[2]);

			list.get(a).add(new Hen(b, c));
		}
		br.close();

		int nk = n + k + 5;
		long[][] d = new long[n][nk];
		int[][] pre = new int[n][nk];
		for (int i = 0; i < n; i++) {
			Arrays.fill(d[i], Long.MAX_VALUE);
		}
		d[s][0] = x[s];
		PriorityQueue<Node> que = new PriorityQueue<Node>();
		Node first = new Node(s, 0, x[s]);
		que.add(first);

		while (!que.isEmpty()) {
			Node cur = que.poll();
			if (cur.d > d[cur.v][cur.v2]) {
				continue;
			}
			for (Hen hen : list.get(cur.v)) {
				long alt = d[cur.v][cur.v2] + hen.c + x[hen.v];
				int nx2 = cur.v2 + 1;
				if (nx2 < nk && alt < d[hen.v][nx2]) {
					d[hen.v][nx2] = alt;
					pre[hen.v][nx2] = cur.v;
					que.add(new Node(hen.v, nx2, alt));
				}
			}
		}
		long ans = Long.MAX_VALUE;
		int ak = 0;
		for (int i = k - 1; i < d[t].length; i++) {
			if (d[t][i] < ans) {
				ans = d[t][i];
				ak = i;
			}
		}
		if (ans == Long.MAX_VALUE) {
			System.out.println("Impossible");
			return;
		}

		System.out.println("Possible");
		System.out.println(ans);
		List<Integer> his = new ArrayList<>();
		int now = t;
		his.add(now + 1);
		for (int i = ak; i > 0; i--) {
			now = pre[now][i];
			his.add(now + 1);
		}
		System.out.println(his.size());
		StringBuilder sb = new StringBuilder();
		for (int i = his.size() - 1; i >= 0; i--) {
			sb.append(his.get(i)).append(' ');
		}
		sb.deleteCharAt(sb.length() - 1);
		System.out.println(sb.toString());
	}

	static class Hen {
		int v, c;

		public Hen(int v, int c) {
			this.v = v;
			this.c = c;
		}
	}

	static class Node implements Comparable<Node> {
		int v, v2;
		long d;

		public Node(int v, int v2, long d) {
			this.v = v;
			this.v2 = v2;
			this.d = d;
		}

		public int compareTo(Node o) {
			return Long.compare(d, o.d);
		}
	}
}