// (⁠◕⁠ᴗ⁠◕⁠✿⁠)

// #pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define srep(i, s, n) for (ll i = s; i < (n); i++)
#define len(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
using namespace std;
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
template<typename T> using vvv = vv<vc<T>>;
using vi = vc<int>;using vvi = vv<int>; using vvvi = vv<vi>;
using ll = long long;using vl = vc<ll>;using vvl = vv<ll>; using vvvl = vv<vl>;
using ld = long double; using vld = vc<ld>; using vvld = vc<vld>; using vvvld = vc<vvld>;
using uint = unsigned int;
using ull = unsigned long long;
const ld pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
// const ll mod = 1000000007;
const ll mod = 998244353;
inline bool inside(ll y, ll x, ll H, ll W) {return 0 <= (y) and (y) < (H) and 0 <= (x) and (x) < (W); }

#define debug(var)  do{std::cout << #var << " : \n";view(var);}while(0)
template<typename T> void view(T e){cout << e << endl;}
template<typename T> void view(const vc<T>& v){for(const auto& e : v){ cout << e << " "; } cout << endl;}
template<typename T> void view(const vv<T>& vv){ for(const auto& v : vv){ view(v); } }

tuple<vl, vi> dijkstra(int s, int N, vv<pair<int, ll>> &g){
    using P = pair<ll, int>;
    vl dist(N, INF);
    vi bef(N);
    priority_queue<P, vc<P>, greater<P>> q;
    dist[s] = 0;
    q.push({0, s});
    while (!q.empty()){
        auto [c, now] = q.top();q.pop();
        if (dist[now] < c) continue;
        for (auto&& [nxt, nc]: g[now]) if (dist[nxt] > c + nc){
            dist[nxt] = c + nc;
            bef[nxt] = now;
            q.push({dist[nxt], nxt}); 
        }
    }
    return {dist, bef};
}

int main(){
    int N, M, K; cin >> N >> M >> K;
    vl C(M); rep(i, M) cin >> C[i];
    vv<pair<int, ll>> g(N * (K + 1));
    rep(i, M){
        int u, v; cin >> u >> v; u--; v--;
        rep(j, K + 1){
            g[u * (K + 1) + j].push_back({v * (K + 1) + j, C[i]});
            g[v * (K + 1) + j].push_back({u * (K + 1) + j, C[i]});
        }
        rep(j, K){
            g[u * (K + 1) + j].push_back({v * (K + 1) + j + 1, 0});
            g[v * (K + 1) + j].push_back({u * (K + 1) + j + 1, 0});
        }
    }
    auto [dist, bef] = dijkstra(0, N * (K + 1), g);
    ll ans = INF;
    rep(j, K + 1) ans = min(ans, dist[(N - 1) * (K + 1) + j]);
    if (ans == INF) cout << -1 << endl;
    else cout << ans << endl;
}