#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> edge;

typedef pair<ll,edge> Data;

const ll INF = (1LL<<60);
ll ans=INF;

ll N,M,K;
vector<edge> g[100000];
ll d[100000][4];


ll cost[100000];

int main(){
  scanf("%lld %lld %lld",&N,&M,&K);
  for(int i=0;i<M;i++)scanf("%lld",&cost[i]);
  
  for(int i=0;i<M;i++){
    ll a,b;
    scanf("%lld %lld",&a,&b);
    a--,b--;
    g[a].push_back( edge(b,cost[i]) );
    g[b].push_back( edge(a,cost[i]) );
  }
  
  for(int i=0;i<N;i++){
    for(int j=0;j<=K;j++){
      d[i][j]=INF;
    }
  }

  priority_queue< Data, vector<Data>, greater<Data> > que;
  que.push( Data(0,edge(0,K) ) );
  d[0][K]=0;
  while(!que.empty()){
    Data dat = que.top();
    que.pop();
    ll pos = dat.second.first;
    ll tk = dat.second.second;
    ll cost = dat.first;
    
    if(pos==N-1)ans=min(ans,cost);
    
    if(d[pos][tk]<cost)continue;
    
    for(int i=0;i<(int)g[pos].size();i++){
      ll to = g[pos][i].first;
      ll ncost = cost + g[pos][i].second;
      if( d[to][tk] > ncost ){
        d[to][tk]=ncost;
        que.push( Data(ncost,edge(to,tk)) );
      }
      
      ll nk=tk-1;
      if(nk>=0){
        if( d[to][nk] > cost ){
          d[to][nk]=cost;
          que.push( Data(cost,edge(to,nk)) );
        } 
      }
    }
  }
  if(ans==INF)ans=-1;
  cout<<ans<<endl;
  return 0;
}