#include <bits/stdc++.h>
//#include <atcoder/modint>

using namespace std;
//using namespace atcoder;
using ll = long long;
//using mint = modint998244353;

template<typename T> using pq = priority_queue<T, vector<T>, greater<T>>;

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    ll N, M, K;
    cin >> N >> M >> K;
    vector<ll> C(M);
    for (int i=0; i<M; i++) cin >> C[i];

    vector<vector<pair<ll, ll>>> E(N);
    for (int i=0; i<M; i++){
        int u, v;
        cin >> u >> v; u--; v--;
        E[u].push_back({v, C[i]});
        E[v].push_back({u, C[i]});
    }
    vector vst(N, vector<bool>(K+1));
    vector dist(N, vector<ll>(K+1, 1e18));
    pq<tuple<ll, ll, ll>> que;
    dist[0][0] = 0;
    que.push({0, 0, 0});

    while(!que.empty()){
        auto [d, from, num] = que.top();
        que.pop();
        if (vst[from][num]) continue;
        vst[from][num] = 1;
        for (auto [to, c] : E[from]){
            if (d+c<dist[to][num]){
                dist[to][num] = d+c;
                que.push({d+c, to, num});
            }
            if (num+1<=K && d<dist[to][num+1]){
                dist[to][num+1] = d;
                que.push({d, to, num+1});
            }
        }
    }
    ll ans=1e18;
    for (int i=0; i<=K; i++) ans = min(ans, dist[N-1][i]);
    if (ans == 1e18) ans = -1;
    cout << ans << endl;

    return 0;
}