#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

const ll INF = 1e18;
void solve() {
  ll n, m, k;
  cin >> n >> m >> k;
  vector g(n * (k + 1), vector<pair<ll, ll>>());
  {
    vector<ll> c(m);
    rep(i, m) cin >> c[i];
    rep(i, m) {
      ll u, v;
      cin >> u >> v, u--, v--;
      rep(j, k + 1) {
        g[n * j + u].emplace_back(n * j + v, c[i]);
        g[n * j + v].emplace_back(n * j + u, c[i]);
      }
      rep(j, k) {
        g[n * j + u].emplace_back(n * (j + 1) + v, 0);
        g[n * j + v].emplace_back(n * (j + 1) + u, 0);
      }
    }
  }
  vector<ll> dist(n * (k + 1), INF);
  priority_queue<pair<ll, ll>> que;
  dist[0] = 0;
  que.emplace(0, 0);
  while (!que.empty()) {
    auto [d, u] = que.top();
    que.pop();
    d = -d;
    if (dist[u] < d)
      continue;
    for (const auto &[v, c] : g[u]) {
      if (dist[v] <= dist[u] + c)
        continue;
      dist[v] = dist[u] + c;
      que.emplace(-dist[v], v);
    }
  }
  ll ans = INF;
  rep(j, k + 1) ans = min(ans, dist[n * j + n - 1]);
  if (ans == INF)
    ans = -1;
  cout << ans << '\n';
}

int main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  int T = 1;
  for (int t = 0; t < T; t++) {
    solve();
  }
  return 0;
}