#include <bits/stdc++.h>
using namespace std;

#define REP(i,n) for(ll i=0;i<(ll)n;i++)
#define dump(x)  cerr << "Line " << __LINE__ << ": " <<  #x << " = " << (x) << "\n";
#define spa << " " <<
#define fi first
#define se second
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()

using ld = long double;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<ld, ld>;

template<typename T> using V = vector<T>;
template<typename T> using P = pair<T, T>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){os << "(" << v.first << ", " << v.second << ")"; return os;}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<vector<T>> &v){ for(auto &e : v){os << e << "\n";} return os;}
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;

template <class T> void UNIQUE(vector<T> &x) {sort(ALL(x));x.erase(unique(ALL(x)), x.end());}
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
void fail() { cout << -1 << '\n'; exit(0); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
template<typename T> void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cerr<<v[i][0];for(ll j=1;j<w;j++)cerr spa v[i][j];cerr<<"\n";}};
template<typename T> void debug(vector<T>&v,ll n){if(n!=0)cerr<<v[0];
for(ll i=1;i<n;i++)cerr spa v[i];
cerr<<"\n";};

const ll INF = (1ll<<62);
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
const ll mod = (int)1e9 + 7;
//const ll mod = 998244353;

template< typename T >
struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WeightedGraph = vector< Edges< T > >;
using UnWeightedGraph = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;

template< typename T >
tuple<vector<T>, vector<int>>  Dijkstra(WeightedGraph< T > &g, int s) {
  // const auto INF = numeric_limits< T >::max();
  vector< T > dist(g.size(), INF);

  using Pi = pair< T, int >;
  priority_queue< Pi, vector< Pi >, greater< Pi > > que;
  dist[s] = 0;
  que.emplace(dist[s], s);

  vector<int> prev(g.size(), -1);

  while(!que.empty()) {
    T cost;
    int idx;
    tie(cost, idx) = que.top();
    que.pop();
    if(dist[idx] < cost) continue;
    for(auto &e : g[idx]) {
      auto next_cost = cost + e.cost;
      if(dist[e.to] <= next_cost) continue;
      dist[e.to] = next_cost;
      que.emplace(dist[e.to], e.to);
      prev[e.to] = idx;
    }
  }

  return {dist, prev};
}

int main(){

    ll N, S, T, K;
    cin >> N >> S >> T >> K;
    S--, T--;
    V<ll> X(N);
    REP(i, N) cin >> X[i];
    ll M;
    cin >> M;
    V<ll> A(M), B(M), Y(M);
    REP(i, M) cin >> A[i] >> B[i] >> Y[i], A[i]--, B[i]--;

    ll L = K;

    auto encode = [&](ll pos, ll k){
        return k * N + pos;
    };

    WeightedGraph<ll> G(N * L);

    REP(i, M){
        REP(j, L-1){
            auto from = encode(A[i], j);
            auto to = encode(B[i], j+1);
            G[from].emplace_back(to, Y[i] + X[B[i]]);
        }
        auto from = encode(A[i], L-1);
        auto to = encode(B[i], L-1);
        G[from].emplace_back(to, Y[i] + X[B[i]]);
    }

    auto [dist, prev] = Dijkstra(G, encode(S, 0));


    ll mi = dist[encode(T, K-1)];
    ll idx = encode(T, K-1);

    if(mi == INF){
        cout << "Impossible\n";
        return 0;
    }

    cout << "Possible\n";
    vector<int> path;
    int now = idx;
    while(now != -1){
        path.push_back(now);
        now = prev[now];
    }
    reverse(ALL(path));

    cout << mi + X[S] << endl;
    
    // dump(path)
    cout << path.size() << endl;
    for(auto x: path){
        cout << x%N+1 << " ";
    }
    cout << endl;

    // for(auto x: path){
    //     cout << x/N spa x%N << endl;
    // }

    return 0;
}