#include <iostream>
#include <algorithm>
#include <functional>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <bitset>
#include <array>
#include<utility>
#include<stack>
#include <iomanip>
//#include<atcoder/all>
//using namespace atcoder;
using namespace std;
#define P pair<int,int>
#define Graph vector<vector<int>>
#define float long double
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define repi(itr,m) for(auto itr=(m).begin();itr!=(m).end();itr++)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define vi vector<int>
#define int long long
const int INF=1e18;
int dx[8]={0,1,0,-1,-1,-1,1,1};
int dy[8]={1,0,-1,0,-1,1,-1,1};
template<typename T> inline bool chmax(T &a, T b) { return ((a < b) ? (a = b, true) : (false));}
template<typename T> inline bool chmin(T &a, T b) { return ((a > b) ? (a = b, true) : (false));}
struct point{
  int x,y;
};
void yn(bool t){
  if(t)cout<<"Yes"<<endl;
  else cout<<"No"<<endl;
}

int solve(){
  int n,m,k;cin>>n>>m>>k;
  vector<int>c(m+1);
  rep(i,1,m+1)cin>>c[i];
  vector<vector<P>>g(n+1);
  rep(i,1,m+1){
    int u,v;cin>>u>>v;
    g[u].push_back({v,c[i]});
    g[v].push_back({u,c[i]});
  }
  vector<vector<int>>dist(k+1,vector<int>(n+1,INF));
  dist[0][1]=0;
  priority_queue<tuple<int,int,int>,vector<tuple<int,int,int>>,greater<tuple<int,int,int>>>pq;
  pq.push({0,0,1});
  
  while(!pq.empty()){
    auto [val,num,p]=pq.top();pq.pop();
    if(dist[num][p]<val)continue;
    if(num!=k){
      for(auto [e,cost]:g[p]){
        if(dist[num+1][e]>val){
          dist[num+1][e]=val;
          pq.push({val,num+1,e});
        }
      }
    }
    for(auto [e,cost]:g[p]){
      if(dist[num][e]>val+cost){
        dist[num][e]=val+cost;
        pq.push({val+cost,num,e});
      }
    }
  }
  int ans=INF;
  rep(i,0,k+1)ans=min(ans,dist[i][n]);
  if(ans==INF){
    cout<<-1<<endl;
    return 0;
  }
  cout<<ans<<endl;
  
  assert(true);
  return 0;
}

signed main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  solve();
}