#include <bits/stdc++.h>
using namespace std;
using lii = pair<long long,pair<int,int>>;

const long long inf = 1001001001001001001;

bool chmin(long long &x,long long y) {
    if(x > y) {
        x = y;
        return true;
    }
    return false;
}

int main() {
    int N,S,T,K;
    cin >> N >> S >> T >> K;
    S--;
    T--;
    vector<int>X(N);
    for(int i = 0; i < N; i++) {
        cin >> X[i];
    }
    int M;
    cin >> M;
    vector<vector<pair<int,int>>>road(N),road2(N);
    for(int i = 0; i < M; i++) {
        int A,B,Y;
        cin >> A >> B >> Y;
        A--;
        B--;
        road[A].push_back({B,Y});
        road2[B].push_back({A,Y});
    }
    vector<vector<long long>>dist(N,vector<long long>(K+1,inf));
    dist[S][1] = X[S];
    priority_queue<lii,vector<lii>,greater<lii>>que;
    que.push({X[S],{S,1}});
    while (!que.empty()) {
        lii x = que.top();
        que.pop();
        long long cost = x.first;
        int n1 = x.second.first;
        int n2 = x.second.second;
        if(dist[n1][n2] != cost) {
            continue;
        }
        n2 = min(K,n2+1);
        for(int i = 0; i < road[n1].size(); i++) {
            int nxt = road[n1][i].first;
            long long cost2 = cost+road[n1][i].second+X[nxt];
            if(chmin(dist[nxt][n2],cost2)) {
                que.push({cost2,{nxt,n2}});
            }
        }
    }
    if(dist[T][K] == inf) {
        cout << "Impossible" << endl;
    }
    else {
        cout << "Possible" << endl;
        cout << dist[T][K] << endl;
        int n1 = T,n2 = K;
        vector<int>ans;
        ans.push_back(T+1);
        while (!(n1 == S && n2 == 1)) {
            for(int i = 0; i < road2[n1].size(); i++) {
                int nxt = road2[n1][i].first;
                long long cost = road2[n1][i].second+X[n1];
                if(dist[nxt][n2-1]+cost == dist[n1][n2]) {
                    ans.push_back(nxt+1);
                    n1 = nxt;
                    n2 = n2-1;
                    break;
                }
                if(dist[nxt][n2]+cost == dist[n1][n2]) {
                    ans.push_back(nxt+1);
                    n1 = nxt;
                    n2 = n2;
                    break;
                }
            }
        }
        reverse(ans.begin(),ans.end());
        cout << ans.size() << endl;
        for(int i = 0; i < ans.size(); i++) {
            cout << ans[i] << ((i+1 == ans.size())?"\n":" ");
        }
    }
}