#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1LL << 60;

struct Edge {
    int to;
    ll cost;
};

int main() {
    int N, M, K;
    cin >> N >> M >> K;

    vector<ll> C(M);
    for (int i = 0; i < M; ++i) {
        cin >> C[i];
    }

    vector<vector<Edge>> G(N + 1);
    for (int i = 0; i < M; ++i) {
        int u, v;
        cin >> u >> v;
        G[u].push_back({v, C[i]});
        G[v].push_back({u, C[i]});
    }

    vector<vector<ll>> dist(N + 1, vector<ll>(K + 1, INF));
    dist[1][0] = 0;

    using T = tuple<ll, int, int>;
    priority_queue<T, vector<T>, greater<>> pq;
    pq.emplace(0, 1, 0);

    while (!pq.empty()) {
        auto [cost, now, used] = pq.top(); pq.pop();

        if (dist[now][used] < cost) continue;

        for (auto& e : G[now]) {
            if (dist[e.to][used] > cost + e.cost) {
                dist[e.to][used] = cost + e.cost;
                pq.emplace(dist[e.to][used], e.to, used);
            }
            if (used < K && dist[e.to][used + 1] > cost) {
                dist[e.to][used + 1] = cost;
                pq.emplace(cost, e.to, used + 1);
            }
        }
    }

    ll ans = *min_element(dist[N].begin(), dist[N].end());
    if (ans == INF) cout << -1 << endl;
    else cout << ans << endl;
}