#include <bits/stdc++.h>
#define mp make_pair
#define eb emplace_back
using namespace std;
using ll = long long;
using wgraph = vector<vector<pair<ll, ll>>>;
constexpr ll inf = 2e18;

vector<ll> dijkstra(int start, vector<vector<pair<ll, ll>>>& g) {
    priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> q;
    vector<ll> dist(g.size(), inf);
    dist[start] = 0;
    q.push(mp(0, start));
    while (!q.empty()) {
        auto p = q.top();
        q.pop();
        ll now = p.second;
        if (dist[now] < p.first) continue;
        for (auto& nx : g[now]) {
            if (dist[nx.first] > dist[now] + nx.second) {
                dist[nx.first] = dist[now] + nx.second;
                q.push(mp(dist[nx.first], nx.first));
            }
        }
    }
    return dist;
}

int n,m,u,v,k,c[200000];
int main() {
    cin >> n >> m >> k;
    wgraph g(n * (k + 1));
    for(int i = 0; i < m; i++){
        cin >> c[i];
    }
    for(int i = 0; i < m; i++){
        cin >> u >> v;
        u--,v--;
        for(int j = 0; j <= k; j++){
            g[n * j + u].eb(mp(n * j + v,c[i]));
            g[n * j + v].eb(mp(n * j + u,c[i]));
            if(j != k){
                g[n * j + u].eb(mp(n * (j + 1) + v,0));
                g[n * j + v].eb(mp(n * (j + 1) + u,0));
            } 
        }
    }
    auto dist = dijkstra(0,g);
    ll ans = inf;
    for(int i = 0; i <= k; i++){
        ans = min(ans,dist[n * i + n - 1]);
    }
    cout << (ans == inf ? -1 : ans) << endl;
}