#include <bits/stdc++.h>
    using namespace std;
    #include <math.h>
    #include <iomanip>
    #include <cstdint>
    #include <string>
    #include <sstream>
    template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
    template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
    #define rep(i,n) for (int i = 0; i < (n); ++i)
    typedef long long ll;
    using P=pair<ll,ll>;
    const ll INF=1e18;
    const int mod=998244353;
    
    struct edge{
        int to;
        ll w;
        edge(int to,ll w):to(to),w(w){}
    };
    
    void solve(){
        int n,s,t,k,m;
        cin>>n>>s>>t>>k;
        s--;t--;
        vector<int>x(n);
        rep(i,n){cin>>x[i];}
        cin>>m;
        vector<vector<edge>>G(n);
        rep(i,m){
            int a,b,y;
            cin>>a>>b>>y;a--;b--;
            G[a].emplace_back(b,x[b]+y);
        }

        vector<vector<ll>>dist(k+1,vector<ll>(n,INF));
        vector<vector<int>>prev(k+1,vector<int>(n,-1));
        vector<vector<int>>prec(k+1,vector<int>(n,-1));
        
        priority_queue<pair<ll,pair<int,int>>,vector<pair<ll,pair<int,int>>>,greater<pair<ll,pair<int,int>>>>q;
        q.push(make_pair(x[s],make_pair(0,s)));
        dist[0][s]=x[s];

        while(!q.empty()){
            int c=q.top().second.first;
            int v=q.top().second.second;
            ll cost=q.top().first;
            q.pop();
            if(cost!=dist[c][v]){continue;}
            for(auto u:G[v]){
                int nc=min(k-1,c+1);
                if(chmin(dist[nc][u.to],cost+u.w)){
                    prev[nc][u.to]=v;
                    prec[nc][u.to]=c;
                    q.push(make_pair(dist[nc][u.to],make_pair(nc,u.to)));
                }
            }
        }

        if(dist[k-1][t]==INF){
            cout<<"Impossible"<<endl;
            return;
        }
        cout<<"Possible"<<endl;
        cout<<dist[k-1][t]<<endl;
        vector<int>ans;
        int p=t,pc=k-1;
        while(pc!=-1){
            ans.push_back(p);
            int np=pc;
            pc=prec[np][p];
            p=prev[np][p];
        }
        reverse(ans.begin(),ans.end());
        cout<<ans.size()<<endl;
        
        rep(i,ans.size()){
            printf("%d%c",ans[i]+1,(i+1<ans.size()?' ':'\n'));
        }
    }
    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        solve();
        return 0;
    }