#include <bits/stdc++.h> 
using namespace std; 
using int128  = __int128_t; 
using int64   = long long; 
using int32   = int; 
using uint128 = __uint128_t; 
using uint64  = unsigned long long; 
using uint32  = unsigned int; 

#define ALL(obj) (obj).begin(),(obj).end() 
template<class T> using priority_queue_reverse = priority_queue<T,vector<T>,greater<T>>; 

constexpr int64 MOD = 1'000'000'000LL + 7; //' 
constexpr int64 MOD2 = 998244353; 
constexpr int64 HIGHINF = 1'000'000'000'000'000'000LL; 
constexpr int64 LOWINF = 1'000'000'000'000'000LL; //' 
constexpr long double PI = 3.1415926535897932384626433L; 

template <class T> vector<T> multivector(size_t N,T init){return vector<T>(N,init);} 
template <class... T> auto multivector(size_t N,T... t){return vector<decltype(multivector(t...))>(N,multivector(t...));} 
template <class T> void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}} 
template <class T, class U>ostream &operator<<(ostream &o, const map<T, U>&obj) {o << "{"; for (auto &x : obj) o << " {" << x.first << " : " << x.second << "}" << ","; o << " }"; return o;} 
template <class T>ostream &operator<<(ostream &o, const set<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;} 
template <class T>ostream &operator<<(ostream &o, const multiset<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;} 
template <class T>ostream &operator<<(ostream &o, const vector<T>&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;} 
template <class T>ostream &operator<<(ostream &o, const deque<T>&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;} 
template <class T, class U>ostream &operator<<(ostream &o, const pair<T, U>&obj) {o << "{" << obj.first << ", " << obj.second << "}"; return o;} 
void print(void) {cout << endl;} 
template <class Head> void print(Head&& head) {cout << head;print();} 
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) {cout << head << " ";print(forward<Tail>(tail)...);} 
template <class T> void chmax(T& a, const T b){a=max(a,b);} 
template <class T> void chmin(T& a, const T b){a=min(a,b);} 
vector<string> split(const string &str, const char delemiter) {vector<string> res;stringstream ss(str);string buffer; while( getline(ss, buffer, delemiter) ) res.push_back(buffer); return res;} 
inline constexpr int msb(int x) {return x?31-__builtin_clz(x):-1;} 
inline constexpr int64 ceil_div(const int64 a,const int64 b) {return (a+(b-1))/b;}// return ceil(a/b) 
void YN(bool flg) {cout << (flg ? "YES" : "NO") << endl;} 
void Yn(bool flg) {cout << (flg ? "Yes" : "No") << endl;} 
void yn(bool flg) {cout << (flg ? "yes" : "no") << endl;} 

/*
 * @title Graph
 * @docs md/graph/Graph.md
 */
template<class T> class Graph{
private:
    const size_t N,H,W;
public:
    vector<vector<pair<size_t,T>>> edges;
    Graph(const size_t N):H(-1),W(-1),N(N), edges(N) {}
    Graph(const size_t H, const size_t W):H(H),W(W),N(H*W), edges(H*W) {}
    inline void make_edge(size_t from, size_t to, T w) {
        edges[from].emplace_back(to,w);
    }
    //{from_y,from_x} -> {to_y,to_x} 
    inline void make_edge(pair<size_t,size_t> from, pair<size_t,size_t> to, T w) {
        make_edge(from.first*W+from.second,to.first*W+to.second,w);
    }
    inline void make_bidirectional_edge(size_t from, size_t to, T w) {
        make_edge(from,to,w);
        make_edge(to,from,w);
    }
    inline void make_bidirectional_edge(pair<size_t,size_t> from, pair<size_t,size_t> to, T w) {
        make_edge(from.first*W+from.second,to.first*W+to.second,w);
        make_edge(to.first*W+to.second,from.first*W+from.second,w);
    }
    inline size_t size(){return N;}
    inline size_t idx(pair<size_t,size_t> yx){return yx.first*W+yx.second;}
};

/** 
 * @url  
 * @est 
 */  
int main() { 
    cin.tie(0);ios::sync_with_stdio(false);
	int N,S,T,K; cin >> N >> S >> T >> K;
	S--,T--;
	vector<int64> X(N);
	for(int i=0;i<N;++i) cin >> X[i];
	int M; cin >> M;
	vector<vector<pair<int,int64>>> edge(N);
	for(int i=0;i<M;++i) {
		int a,b,y; cin >> a >> b >> y;
		--a,--b;
		edge[a].push_back({b,y});
	}
	auto dp = multivector(N,(K+1),LOWINF);
	auto dp2 = multivector(N,K+1,make_pair(-1,-1));
	dp[S][1] = X[S];
	priority_queue_reverse<tuple<int64,int,int>> pq;
	pq.push({dp[S][1],S,1});
	while(pq.size()) {
		auto tp = pq.top(); pq.pop();
		int64 cost = get<0>(tp);
		int from = get<1>(tp);
		int from_cnt = get<2>(tp);
		if(cost > dp[from][from_cnt]) continue;
		int nxt = min(from_cnt+1,K);
		for(auto p:edge[from]) {
			int to = p.first;
			int64 w = p.second;
			
			if(dp[to][nxt] > cost + w + X[to]) {
				dp[to][nxt] = cost + w + X[to];
				dp2[to][nxt] = {from,from_cnt};
				pq.push({dp[to][nxt],to,nxt});
			}
		}
	}
	int ans_K = min_element(dp[T].begin()+K,dp[T].end())-dp[T].begin();
	int64 ans = dp[T][ans_K];
	if(ans>=LOWINF) {
		cout << "Impossible" << endl;
	}
	else {
		cout << "Possible" << endl;
		cout << ans << endl;
		vector<int> P;
		int p = T, q = ans_K;
		while(p!=-1) {
			P.push_back(p+1);
			auto tmp=p,tmq=q;
			p = dp2[tmp][tmq].first;
			q = dp2[tmp][tmq].second;
		}
		reverse(ALL(P));
		cout << P.size() << endl;
		for(int i=0;i<P.size();++i) cout << P[i] << " \n"[i+1==P.size()];
	}
    return 0; 
}