#include<bits/stdc++.h>
#define int long long
using namespace std;
const int inf = 0x3f3f3f3f3f3f3f3f,N = 1000,M = 10000;
int usv;
int bgn[N + 11],to[2 * M + 11],nxt[2 * M + 11],c[2 * M + 11],u[2 * M + 11],idx = 1;
inline void add(int x,int y,int w)
{
	to[++idx] = y,u[idx] = 0,c[idx] = w,nxt[idx] = bgn[x],bgn[x] = idx;
	to[++idx] = x,u[idx] = 0,c[idx] = 0,nxt[idx] = bgn[y],bgn[y] = idx;
}
int deep[N + 11],nbgn[N + 11];
int flow,S,T;
int q[N + 11],l,r;
inline bool BFS()
{
	for(int i = 1;i <= usv;i++) deep[i] = 0,nbgn[i] = bgn[i];
	deep[S] = 1;
	q[l = 0] = S,r = 1;
	while(l ^ r)
	{
		int p = q[l++];
		for(int i = bgn[p];i;i = nxt[i]) if(c[i] ^ u[i])
		{
			int v = to[i];
			if(!deep[v])
				deep[v] = deep[p] + 1,q[r++] = v;
		}
	}
	return deep[T];
}
int DFS(int p,int W)
{
	if(!W || p == T) return W;
	int res = 0;
	for(int& i = nbgn[p];i;i = nxt[i]) if(deep[to[i]] == deep[p] + 1)
	{
		int x = DFS(to[i],min(W,c[i] - u[i]));
		res += x,W -= x,u[i] += x,u[i ^ 1] -= x;
		if(!W) break;
	}
	return res;
}
void Flow()
{
	flow = 0;
	for(int i = 2;i <= idx;i++) u[i] = 0;
	while(BFS())
		flow += DFS(S,inf);
}
int val[211];
int n,m,k,s,t;
long long ans;
set<int> res;
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	cin >> n >> m >> k;
	cin >> s >> t;
	S = s,T = t + n;
	usv = 2 * n;
	for(int i = 1;i <= n;i++)
	{
		cin >> val[i];
		add(i,i + n,val[i]);
	}
	while(m--)
	{
		int x,y;
		cin >> x >> y;
		add(x + n,y,inf);
	}
	BFS();
	if(deep[T] == 0)
	{
		cout << 0;
		return 0;
	}
	if(deep[T] < (k << 1))
	{
		cout << -1;
		return 0;
	} 
	while(k--)
	{
		Flow();
		ans += flow;
		for(int i = 1;i <= n;i++) if(deep[i] && !deep[i + n])
			c[i * 2] = inf,res.insert(i);
	}
	cout << res.size() << "\n";
	for(auto i:res) cout << i << " ";
	return 0;
}