#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
const ll dx[9]={0,1,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

struct Edge{
    ll to,cost;
};
template<typename T>
struct Dijkstra{
    vector<T> dist;
    vector<int> prev;
    Dijkstra(vector<vector<Edge>> &g,int s){
        dist=vector<T>(g.size(),numeric_limits<T>::max()/5);
        prev=vector<int>(g.size(),-1);
        using pi=pair<T,int>;
        priority_queue<pi,vector<pi>,greater<pi>> que;
        dist[s]=0;
        que.emplace(dist[s],s);
        while(!que.empty()){
            T cost;int idx;
            tie(cost,idx)=que.top();que.pop();
            if(dist[idx]!=cost)continue;
            for(auto &e:g[idx]){
                T ncost=cost+e.cost;
                if(dist[e.to]<=ncost)continue;
                prev[e.to]=idx;
                dist[e.to]=ncost;
                que.emplace(dist[e.to],e.to);
            }
        }
    }
    vector<int> get_path(int t){//到達できない場合、return=t;
        vector<int> path;
        for (int cur = t; cur != -1; cur = prev[cur]) {
            path.push_back(cur);
        }
        reverse(path.begin(), path.end());
        return path;
    }
};

int main(){
    ll n,m,k;cin >> n >> m >> k;
    vl c(m);rep(i,m)cin >> c[i];
    vector<vector<Edge>> g(n*(k+1));
    rep(i,m){
        ll u,v;cin >> u >> v;u--;v--;
        rep(j,(k+1)){
            g[u+n*j].push_back({v+n*j,c[i]});
            g[v+n*j].push_back({u+n*j,c[i]});
        }
        rep(j,k){
            g[u+n*j].push_back({v+n*(j+1),0});
            g[v+n*j].push_back({u+n*(j+1),0});
        }
    }
    Dijkstra<ll> dk(g,0);
    ll ans=INF;
    rep(_,(k+1))chmin(ans,dk.dist[n-1+_*n]);
    cout << (ans>=INF/10? -1:ans)<< endl;

}