#include<bits/stdc++.h>
using namespace std;

const int maxn=205;
const int maxm=505;
const int inf=0x3f3f3f3f;

inline int read(){
    int x=0,w=1;char c=getchar();
    while(c<'0'||c>'9'){if(c=='-')w=-1;c=getchar();}
    while(c<='9'&&c>='0'){x=(x<<3)+(x<<1)+c-'0';c=getchar();}
    return x*w;
}

int n,m,k;
int s,t;
int val[maxn];
vector<int> E[maxn];
int d[maxn];
int S,T;
struct edge{
    int to,nxt,w;
}e[maxn*20+maxm*10];
int head[maxn*10],cnt;
inline void add_edge(int u,int v,int w){
    e[++cnt].to=v,e[cnt].nxt=head[u],head[u]=cnt,e[cnt].w=w;
    e[++cnt].to=u,e[cnt].nxt=head[v],head[v]=cnt,e[cnt].w=0;
}
int cur[maxn*10],dis[maxn*10];
int dfs(int u,int rest){
    if(u==T) return rest;
    int flow=0;
    for(int i=cur[u],v,w;i&&rest;i=e[i].nxt){
        cur[u]=i;
        v=e[i].to,w=e[i].w;
        if(dis[u]+1==dis[v]&&w){
            int k=dfs(v,min(rest,w));
            flow+=k,rest-=k;
            e[i].w-=k,e[i^1].w+=k;
        }
    }
    if(!flow) dis[u]=-1;
    return flow;
}
queue<int> q;
inline int MF(){
    int flow=0;
    while(1){
        memcpy(cur,head,sizeof(head));
        memset(dis,-1,sizeof(dis));
        dis[S]=0;
        q.push(S);
        while(!q.empty()){
            int u=q.front();
            q.pop();
            for(int i=head[u],v,w;i;i=e[i].nxt){
                v=e[i].to,w=e[i].w;
                if(dis[v]==-1&&w){
                    dis[v]=dis[u]+1;
                    q.push(v);
                }
            }
        }
        if(dis[T]==-1) return flow;
        flow+=dfs(S,inf);
    }
}

int main(){
    // freopen("apers.in","r",stdin);
    // freopen("apers.out","w",stdout);
    n=read(),m=read(),k=read();
    s=read(),t=read();
    S=2*k*n+1,T=2*k*n+2;
    cnt=1;
    add_edge(S,s,inf),add_edge((2*k-1)*n+t,T,inf);
    for(int i=1;i<=n;++i){
        val[i]=read();
        for(int j=1;j<=k;++j){
            add_edge((2*j-2)*n+i,(2*j-1)*n+i,val[i]);
            if(j<k) add_edge((2*j-2)*n+i,(2*j+1)*n+i,inf);
        }
    }
    for(int i=1,u,v;i<=m;++i){
        u=read(),v=read();
        E[u].push_back(v);
        for(int j=1;j<=k;++j){
            add_edge((2*j-1)*n+u,(2*j-2)*n+v,inf);
        }
    }
    queue<int> q;
    memset(d,0x3f,sizeof(d));
    q.push(s);
    while(!q.empty()){
        int u=q.front();
        q.pop();
        for(int v:E[u]){
            if(d[v]==inf){
                d[v]=d[u]+1;
                q.push(v);
            }
        }
    }
    if(d[t]<k) return printf("-1\n"),0;
    int flow=MF();
    if(flow==inf) flow=-1;
    printf("%d\n",flow);
    return 0;
}