#include "bits/stdc++.h"
#define For(i,a,b) for(int i=a;i<=b;i++)
#define Rev(i,a,b) for(int i=a;i>=b;i--)
#define Fin(file) freopen(file,"r",stdin)
#define Fout(file) freopen(file,"w",stdout)
#define assume(expr) ((!!(expr))||(exit((fprintf(stderr,"Assumption Failed: %s on Line %d\n",#expr,__LINE__),-1)),false))
using namespace std;
// N is the number of vertices, M is the number of edges you're about to add
// cst_type is what you think it is
template<int N,int M,typename cst_type=int>
class Dinic{
    int n,S,T,head[N],nxt[M*2],to[M*2],tot,q[N],h,t,dep[N],now[N]; cst_type cap[M*2],maxflow;
    bool bfs(){
        h=t=0; q[t++]=S; For(i,1,n) dep[i]=0; ; dep[S]=1; now[S]=head[S];
        while(h<t){
            int u=q[h++]; for(int e=head[u];e;e=nxt[e]){
                if(cap[e]==0) continue; ; int v=to[e];
                if(!dep[v]) { dep[v]=dep[u]+1; now[v]=head[v]; q[t++]=v; if(v==T) return true; }
            }
        } return false;
    }
    cst_type dfs(int u,cst_type flow){
        if(u==T) return flow; ; cst_type fw=0;
        for(int& e=now[u];e;e=nxt[e]){
            if(cap[e]==0) continue; ; int v=to[e]; if(dep[v]!=dep[u]+1) continue;
            cst_type res=dfs(v,min(flow,cap[e])); if(res==0) { dep[v]=0; continue; }
            cap[e]-=res; cap[e^1]+=res; fw+=res; flow-=res; if(flow==0) break;
        } return fw;
    }
public:
    void init(int _n) { n=_n; tot=1; } 
    void clear(int _n) { For(i,1,n) head[i]=0; ; maxflow=0; n=_n; tot=1; }
    int add_edge(int x,int y,cst_type z) { nxt[++tot]=head[x]; head[x]=tot; to[tot]=y; cap[tot]=z; nxt[++tot]=head[y]; head[y]=tot; to[tot]=x; cap[tot]=0; return tot-1; }
    cst_type solve(int _S,int _T,cst_type inf=numeric_limits<cst_type>::max()){
        if(!n||tot%2==0) { cerr<<"INIT YOUR DINIC!!!!!!!!!!!!"<<endl; exit(-1); }
        S=_S; T=_T; while(bfs()) { cst_type res=-1; while((res=dfs(S,inf))!=0) maxflow+=res; } ; return maxflow;
    }
    cst_type flowing(int e) { return cap[e^1]; }
    vector<int> get_cut() { bfs(); vector<int> res; for(int e=2;e<=tot;e+=2) if(dep[to[e^1]]&&!dep[to[e]]) res.push_back(e); ; return res; }
};
const int N=205,M=505; typedef long long ll;
Dinic<N*5*2,M*5+N*5*2,ll> G;
int n,m,__ssa,K,S0,T0,a[N],in[N][6],out[N][6],ncnt,id[N*12];
signed main(){
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    cin>>n>>m>>K>>S0>>T0; __ssa=1; For(i,1,n) cin>>a[i],__ssa+=a[i];; For(i,1,n) For(j,0,K-1) in[i][j]=++ncnt,out[i][j]=++ncnt;
    G.init(ncnt); For(i,1,n) { For(j,0,K-1) id[G.add_edge(in[i][j],out[i][j],a[i])]=i;; For(j,0,K-2) G.add_edge(in[i][j],out[i][j+1],__ssa); }
    For(j,0,K-2) G.add_edge(out[T0][j],out[T0][j+1],__ssa);; For(i,1,m) { int x,y; cin>>x>>y; For(j,0,K-1) G.add_edge(out[x][j],in[y][j],__ssa); }
    ll res=G.solve(in[S0][0],out[T0][K-1]); 
    // printf("res=%lld\n",res);
    if(res>=__ssa) cout<<"-1\n",exit(0);
    vector<int> Cut=G.get_cut(); cout<<Cut.size()<<'\n'; for(int c:Cut) cout<<id[c]<<' ';; cout<<'\n';
    cerr<<"Time = "<<clock()<<" ms"<<endl;
    return 0;
}

// START TYPING IF YOU DON'T KNOW WHAT TO DO