#include <bits/stdc++.h>
using namespace std;
#define int long long
//頂点倍加ダイクストラ
signed main(){
    int n,m,k;cin>>n>>m>>k;
    vector<int>c(m);
    for(int i=0;i<m;i++)cin>>c[i];
    vector<vector<vector<tuple<int,int,int>>>>connect(n,vector<vector<tuple<int,int,int>>>(k+1));
    for(int i=0;i<m;i++){
        int a,b;cin>>a>>b;
        a--;b--;
        //connect[i][j]->頂点i にいてj まいクーポン使った
        for(int j=0;j<k;j++){
            connect[a][j].push_back({b,j,c[i]});
            connect[a][j].push_back({b,j+1,0});
            connect[b][j].push_back({a,j,c[i]});
            connect[b][j].push_back({a,j+1,0});
        }
        connect[a][k].push_back({b,k,c[i]});
        connect[b][k].push_back({a,k,c[i]});
    }
    priority_queue<tuple<int,int,int>>que;
    const int inf=1e18;
    vector<vector<int>>dist(n,vector<int>(k+1,inf));
    vector<vector<bool>>vis(n,vector<bool>(k+1,false));
    dist[0][0]=0;
    que.push({0,0,0});
    while(!que.empty()){
        auto[w,a,b]=que.top();
        w*=-1;
        que.pop();
        if(vis[a][b])continue;
        if(dist[a][b]>w)continue;
        vis[a][b]=true;
        for(auto[ta,tb,ww]:connect[a][b]){
            if(!vis[ta][tb]){
                if(dist[ta][tb]>dist[a][b]+ww){
                    dist[ta][tb]=dist[a][b]+ww;
                    que.push({-dist[ta][tb],ta,tb});
                }
            }
        }
    }
    int ans=inf;
    for(int i=0;i<=k;i++){
        ans=min(ans,dist[n-1][i]);
    }
    cout<<(ans==inf?-1:ans)<<endl;
}