#include <bits/stdc++.h>
using namespace std;
//#include<atcoder/all>
//using namespace atcoder;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
constexpr ll MAX = 2000000000000000000;
constexpr ld PI = 3.14159265358979;
constexpr ll MOD = 0;//2024948111;
ld dotorad(ld K){ return PI * K / 180.0; }
ld radtodo(ld K){ return K * 180.0 / PI; }
mt19937 mt;
void randinit(){ srand((unsigned)time(NULL));mt = mt19937(rand()); }
int main(){
    ll N,M,K;
    cin >> N >> M >> K;
    vector<ll> CC(M);
    for(ll i = 0; i < M; i++){
        cin >> CC[i];
    }
    vector<vector<ll>> G(N),C(N);
    for(ll i = 0; i < M; i++){
        ll a,b;
        cin >> a >> b;
        a--;b--;
        G[a].emplace_back(b);
        G[b].emplace_back(a);
        C[a].emplace_back(CC[i]);
        C[b].emplace_back(CC[i]);
    }

    vector<vector<ll>> memo(K + 1,vector<ll>(N,MAX));
    priority_queue<tuple<ll,ll,ll>,vector<tuple<ll,ll,ll>>,greater<tuple<ll,ll,ll>>> que;
    que.emplace(0,0,0);
    while(!que.empty()){
        auto [cost,rank,now] = que.top();
        que.pop();
        if(memo[rank][now] <= cost) continue;
        memo[rank][now] = cost;
        for(ll i = 0; i < G[now].size(); i++){
            ll next = G[now][i],c = C[now][i];
            if(rank + 1 <= K){
                que.emplace(cost,rank + 1,next);
            }
            que.emplace(cost + c,rank,next);
        }
    }
    ll ans = MAX;
    for(ll i = 0; i <= K; i++){
        ans = min(ans,memo[i][N - 1]);
    }
    if(ans == MAX) cout << -1 << endl;
    else cout << ans << endl;

}