#include<bits/stdc++.h>

using namespace std;
typedef long long ll;

const ll V = 2000 + 5, E = 1e6 + 5, Inf = 0x3f3f3f3f3f3f3f3f;
ll tot = 0, ver[E] = {}, cap[E] = {}, dis[V] = {}, cur[V] = {}, col[V] = {};
vector<ll> G[V] = {};
queue<ll> Q;

inline bool bfs(ll s, ll t){
	memset(dis, 0x3f, sizeof(dis)), memset(cur, 0, sizeof(cur));
	dis[s] = 0;
	Q.push(s);
	while(Q.size()){
		ll u = Q.front(); Q.pop();
		for(ll i = 0 ; i < (ll)G[u].size() ; i ++){
			ll e = G[u][i], v = ver[e];
			if(dis[v] == Inf && cap[e]){
				dis[v] = dis[u] + 1;
				Q.push(v);
			}
		}
	}
	return dis[t] != Inf;
}

inline ll dfs(ll u, ll t, ll f){
	if(u == t || !f) return f;
	ll ret = 0;
	for(ll &i = cur[u] ; i < (ll)G[u].size() ; i ++){
		ll e = G[u][i], v = ver[e];
		if(cap[e] && dis[v] == dis[u] + 1){
			ll x = dfs(v, t, min(cap[e], f - ret));
			if(x) ret += x, cap[e] -= x, cap[e ^ 1] += x;
		}
		if(ret == f) return ret;
	}
	return ret;
}

inline void addedge(ll u, ll v, ll w){
	G[u].push_back(tot), ver[tot] = v, cap[tot] = w, tot ++;
	G[v].push_back(tot), ver[tot] = u, cap[tot] = 0, tot ++;
}

inline void paint(ll u){
	col[u] = 1;
	for(ll e : G[u]){
		ll v = ver[e], w = cap[e];
		if(w && !col[v]) paint(v);
	}
}

inline ll dinic(ll s, ll t){
	ll ret = 0;
	while(bfs(s, t)){
		ret += dfs(s, t, Inf);
		if(ret >= Inf){
			printf("-1");
			exit(0);
		}
	}
	paint(s);
	return ret;
}

ll n = 0, m = 0, k = 0, s = 0, t = 0;
vector<ll> ans;

int main(){
	scanf("%lld %lld %lld", &n, &m, &k); k --;
	scanf("%lld %lld", &s, &t); s --, t --;
	for(ll i = 0, c = 0 ; i < n ; i ++){
		scanf("%lld", &c);
		for(ll x = 0 ; x <= k ; x ++) addedge((2 * x) * n + i, (2 * x + 1) * n + i, c);
		for(ll x = 0 ; x < k ; x ++) addedge((2 * x) * n + i, (2 * x + 3) * n + i, Inf);
	}
	for(ll x = 0 ; x < k ; x ++) addedge((2 * x + 1) * n + t, (2 * x + 3) * n + t, Inf);
	for(ll i = 0, u = 0, v = 0 ; i < m ; i ++){
		scanf("%lld %lld", &u, &v); u --, v --;
		for(ll x = 0 ; x <= k ; x ++) addedge((2 * x + 1) * n + u, (2 * x) * n + v, Inf);
	}
	dinic(s, (2 * k + 1) * n + t);
	for(ll i = 0 ; i < n ; i ++) for(ll x = 0 ; x <= k ; x ++) if(col[(2 * x) * n + i] != col[(2 * x + 1) * n + i]){
		ans.push_back(i);
		break;
	}
	printf("%lld\n", (ll)ans.size());
	for(ll x : ans) printf("%lld ", x + 1);
	return 0;
}