#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)
#define all(a) (a).begin(),(a).end()

const ll INF = 1ll << 60;

template<typename T> bool chmin(T& a, const T& b) {
    if (a > b) {
        a = b;
        return true;
    }
    else return false;
}

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    
    int N, M, K;
    cin >> N >> M >> K;
    vector<ll> C(M);
    rep(i, 0, M) cin >> C[i];
    vector<vector<pair<int, int>>> G(N);
    rep(i, 0, M) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        G[u].push_back({v, i});
        G[v].push_back({u, i});
    }
    
    vector dist(K + 1, vector<ll>(N, INF));
    priority_queue<pair<ll, pair<int, int>>, vector<pair<ll, pair<int, int>>>, greater<pair<ll, pair<int, int>>>> que;
    dist[K][0] = 0;
    que.push({0, {K, 0}});
    
    while (!que.empty()) {
        ll d = que.top().first;
        int k = que.top().second.first;
        int v = que.top().second.second;
        que.pop();
        
        if (d > dist[k][v]) continue;
        
        for (pair<int, int> e : G[v]) {
            if (k != 0) {
                if (chmin(dist[k - 1][e.first], dist[k][v])) {
                    que.push({dist[k - 1][e.first], {k - 1, e.first}});
                }
            }
            
            if (chmin(dist[k][e.first], dist[k][v] + C[e.second])) {
                que.push({dist[k][e.first], {k, e.first}});
            }
        }
    }
    
    ll ans = INF;
    rep(i, 0, K + 1) ans = min(ans, dist[i][N - 1]);
    
    cout << (ans == INF ? -1 : ans) << '\n';
}