#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;

#include<queue>
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll n,s,t,k;
    cin>>n>>s>>t>>k;
    s--;t--;
    vector<ll> x(n);
    for(int i = 0;i<n;i++) cin>>x[i];
    vector<vector<pair<ll,ll>>> g(n);
    int m;
    cin>>m;
    for(int i = 0;i<m;i++){
        ll a,b,y;
        cin>>a>>b>>y;
        a--;b--;
        g[a].push_back(make_pair(b,y));
    }
    vector<vector<ll>> dp(n,vector<ll>(k+1,1e18));
    vector<vector<pair<ll,ll>>> prev(n,vector<pair<ll,ll>>(k+1,make_pair(-1,-1)));
    dp[s][1] = x[s];
    using dat = pair<ll,pair<ll,ll>>;
    priority_queue<dat,vector<dat>,greater<dat>> que;
    que.push({x[s],{s,1}});

    while(que.size()){
        auto now = que.top();
        que.pop();
        int ni = now.second.first;
        int t = now.second.second;
        if(dp[ni][t]!=now.first) continue;
        for(auto itr:g[ni]){
            int to = itr.first;
            ll cost = now.first + itr.second + x[to];
            int nt = t + 1;
            if(nt>k) nt = k;
            if(dp[to][nt]<=cost) continue;
            dp[to][nt] = cost;
            prev[to][nt] = make_pair(ni,t);
            que.push({cost,{to,nt}});
        }
    }

    if(dp[t][k]==1e18){
        cout<<"Impossible\n";
        return 0;
    }
    cout<<"Possible\n";
    cout<<dp[t][k]<<endl;
    vector<int> ans;
    ll ni = t;
    ll p = k;
    ans.push_back(ni);
    while(true){
        auto nxt = prev[ni][p];
        if(nxt.first==-1) break;
        ni = nxt.first;
        p = nxt.second;
        ans.push_back(ni);
    }
    cout<<ans.size()<<endl;
    reverse(ans.begin(),ans.end());
    for(int i = 0;i<ans.size();i++){
        if(i) cout<<" ";
        cout<<ans[i]+1;
    }
    cout<<endl;
}