#include <bits/stdc++.h>
using namespace std;
#define rep(i, x, limit) for (long long i = (long long)x; i < (long long)limit; i++)
#define REP(i, x, limit) for (long long i = (long long)x; i <= (long long)limit; i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define el '\n'
#define spa " "
#define Yes cout << "Yes" << el
#define No cout << "No" << el
#define YES cout << "YES" << el
#define NO cout << "NO" << el
#define eps (1e-10)
#define Equals(a,b) (fabs((a) - (b)) < eps )
#define debug(x) cerr << #x << " = " << x << el
using ll = long long;
using ull = unsigned long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using vs = vector<string>;
using vb = vector<bool>;
const double pi = 3.141592653589793238;
const int inf = 1073741823;
const ll infl = 1LL << 60;
const string ABC = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const string abc = "abcdefghijklmnopqrstuvwxyz";
const ll MOD = 998244353;
#include<atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using vm = vector<mint>;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll n,m,k;cin>>n>>m>>k;
  vl C(m);
  rep(i,0,m)cin>>C[i];
  vector<vector<pll>> G(n);
  rep(i,0,m){
    ll u,v;cin>>u>>v;
    u--;v--;
    G[u].emplace_back(v,C[i]);
    G[v].emplace_back(u,C[i]);
  }
  vvl D(k+1,vl(n,infl));
  using T=tuple<ll,ll,ll>;
  priority_queue<T,vector<T>,greater<T>> pq;
  pq.push({0,0,0});
  while(!pq.empty()){
    auto[d,u,used]=pq.top();pq.pop();
    if(D[used][u]<=d)continue;
    D[used][u]=d;
    for(auto[v,cost]:G[u]){
      if(D[used][v]>d+cost){
        pq.push({d+cost,v,used});
      }
      if(used+1<=k&&D[used+1][v]>d){
        pq.push({d,v,used+1});
      }
    }
  }
  ll ans=infl;
  rep(i,0,k+1)ans=min(ans,D[i][n-1]);
  if(ans==infl)ans=-1;
  cout<<ans<<el;
}