#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll I=1167167167167167167;
ll Q=1e9+7;
#define rep(i,a) for (ll i=0;i<a;i++)
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
template<class T> void print_tate(vector<T> &v) {rep(i,v.size()) cout<<v[i]<<"\n";}
void yneos(bool a){if(a) cout<<"Yes"<<"\n"; else cout<<"No"<<"\n";}
ll N,S,T,K;
ll p[111111];

int where[1234567];

using len_type=ll;
struct edge{
    ll to;
	len_type length;
};

len_type dijkstra_movement(edge e,int from,len_type t){
    return t+p[e.to%N]+e.length;
}

//距離INF＝1167167167167167167
vector<len_type> dijkstra(vector<vector<edge>> &G,int start){
    int M=G.size();
    assert(M>start&&start>=0);
    vector<len_type> seen(M,1167167167167167167);
    seen[start]=0;
    priority_queue<pair<len_type,int>,vector<pair<len_type,int>>,greater<pair<len_type,int>>> pq;
    pq.push({0,start});
    while(!pq.empty()){
        len_type time;
        int ver;
        tie(time,ver)=pq.top();
        pq.pop();
        if(seen[ver]<time) continue;
        for(edge x:G[ver]){
            len_type T=dijkstra_movement(x,ver,time);
            if(T<seen[x.to]){
				where[x.to]=ver;
                pq.push({T,x.to});
                seen[x.to]=T;
            }
        }
    }
    return seen;
}

//おちこんだりもしたけれど、私はげんきです。
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin>>N>>S>>T>>K;
	S--,T--;
	rep(i,N) cin>>p[i];
	vector<vector<edge>> G(N*(K));
	int M;
	cin>>M;
	rep(i,M){
		ll a,b;
		ll y;
		cin>>a>>b>>y;
		a--,b--;
		G[a+N*(K-1)].push_back({b+N*(K-1),y});
		//G[b+N*(K-1)].push_back({a+N*(K-1),y});
		rep(i,K-1){
			G[a+N*(i)].push_back({b+N*(i+1),y});
			//G[b+N*(i)].push_back({a+N*(i+1),y});
		}
	}
	auto seen=dijkstra(G,S);
	//rep(i,N*K) cout<<seen[i]<<endl;
	if(seen[N*(K-1)+T]==I){
		cout<<"Impossible\n";
		return 0;
	}
	int A=N*(K-1)+T;
	cout<<"Possible\n";
	cout<<seen[A]+p[S]<<"\n";
	vector<int> ans={A};
	while(A!=S){
		ans.push_back(where[A]);
		A=where[A];
	}
	int siz=ans.size();
	cout<<siz<<"\n";
	for(int i=siz-1;i>=0;i--){
		cout<<ans[i]%N+1;
		if(i!=0) cout<<" ";
	}
	cout<<"\n";
	return 0;
}