#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, m, k;
  cin >> n >> m >> k;
  vector<int> c(m);
  rep(i, m) cin >> c[i];
  vector Graph((k + 1) * n, vector<pair<int, ll>>());
  rep(j, m) {
    int u, v;
    cin >> u >> v;
    --u, --v;
    rep(i, k + 1) {
      Graph[i * n + u].push_back({ i * n + v, c[j] });
      Graph[i * n + v].push_back({ i * n + u, c[j] });
      if (i < k) {
        Graph[i * n + u].push_back({ (i + 1) * n + v, 0 });
        Graph[i * n + v].push_back({ (i + 1) * n + u, 0 });
      }
    }
  }
  vector<ll> dist((k + 1) * n, 1e18);
  dist[0] = 0;
  priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<pair<ll, int>>> pq;
  pq.push({ 0, 0 });
  while (!pq.empty()) {
    auto [d, u] = pq.top();
    pq.pop();
    if (d > dist[u]) continue;
    for (auto [v, w] : Graph[u]) {
      if (dist[v] > d + w) {
        dist[v] = d + w;
        pq.push({ dist[v], v });
      }
    }
  }
  ll ans = 1e18;
  rep(i, k + 1) ans = min(ans, dist[i * n + n - 1]);
  if (ans == 1e18) ans = -1;
  cout << ans << '\n';
  return 0;
}