#include<iostream>
#include<algorithm>
#include<queue>
#include<vector>
using namespace std;
int n,s,t,k,m;
int x[1<<17];
vector<pair<int,int> >G[1<<17];
void solve()
{
	cin>>n>>s>>t>>k;
	s--,t--;
	k--;
	for(int i=0;i<n;i++)cin>>x[i];
	cin>>m;
	for(int i=0;i<m;i++)
	{
		int a,b,c;cin>>a>>b>>c;
		a--,b--;
		G[a].push_back(make_pair(b,c));
	}

        vector<vector<long> >dp(k+1,vector<long>(n,9e18));
	vector<vector<int> >prc(k+1,vector<int>(n,-1));
	vector<vector<int> >pru(k+1,vector<int>(n,-1));
	dp[0][s]=x[s];
	priority_queue<pair<long,pair<int,int> > >P;
	P.push(make_pair(-x[s],make_pair(0,s)));
	while(!P.empty())
	{
		int c=P.top().second.first;
		int u=P.top().second.second;
		long cost=-P.top().first;
		P.pop();
		if(dp[c][u]<cost)continue;
		for(pair<int,int>e:G[u])
		{
			int v=e.first;
			long nxt=cost+e.second+x[v];
			int nc=c==k?c:c+1;
			if(dp[nc][v]>nxt)
			{
				dp[nc][v]=nxt;
				prc[nc][v]=c;
				pru[nc][v]=u;
				P.push(make_pair(-nxt,make_pair(nc,v)));
			}
		}
	}

        if(dp[k][t]==(long)9e18)
	{
		cout<<"Impossible"<<endl;
		return ;
	}
	cout<<"Possible"<<endl;
	cout<<dp[k][t]<<endl;
	vector<int>ans;
	while(k!=-1)
	{
		ans.push_back(t);
		int nk=prc[k][t];
		t=pru[k][t];
		k=nk;
	}
	reverse(ans.begin(),ans.end());
	cout<<ans.size()<<endl;
	for(int i=0;i<ans.size();i++)cout<<ans[i]+1<<(i+1==ans.size()?"\n":" ");
    }
    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        solve();
        return 0;
    }