#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
#define rep3(i, a, b, c) for (ll i = (a); i < (b); i += (c))
#define rep2(i, a, b) rep3(i, a, b, 1)
#define rep1(i, n) rep2(i, 0, n)
#define rep0(n) rep1(aaaaa, n)
#define ov4(a, b, c, d, name, ...) name
#define rep(...) ov4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__)
#define per(i, a, b) for (ll i = (a) - 1; i >= (b); i--)
#define fore(e, v) for (auto&& e : v)
#define all(a) begin(a), end(a)
#define sz(a) (int)(size(a))
#define lb(v, x) (lower_bound(all(v), x) - begin(v))
#define eb emplace_back

template <typename T, typename S>
bool chmin(T& a, const S& b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T, typename S>
bool chmax(T& a, const S& b) {
  return a < b ? a = b, 1 : 0;
}
const int INF = 1e9 + 100;
const ll INFL = 3e18 + 100;
#define i128 __int128_t
struct _ {
  _() { cin.tie(0)->sync_with_stdio(0), cout.tie(0); }
} __;

int main() {
  int N, M, K;
  cin >> N >> M >> K;
  vector G(N, vector<pll>());
  vl C(M);
  fore(i, C) cin >> i;
  rep(i, M) {
    int U, V;
    cin >> U >> V;
    --U, --V;
    G[U].eb(pll{V, C[i]});
    G[V].eb(pll{U, C[i]});
  }
  vl dist(N * (K + 1), 1e18);
  using al2 = array<ll, 2>;
  dist[0] = 0;
  priority_queue<al2, vector<al2>, greater<al2>> pq;
  pq.push({0, 0});
  while (pq.size()) {
    auto [d, x] = pq.top();
    pq.pop();
    if (d > dist[x]) continue;
    ll ticket = x / N, v = x % N;
    if (ticket < K) {
      for (auto [u, _] : G[v]) {
        int y = u + N * (ticket + 1);
        if (dist[y] > d) {
          dist[y] = d;
          pq.push(al2{d, y});
        }
      }
      if (dist[x + N] > d) {
        dist[x + N] = d;
        pq.push(al2{d, x + N});
      }
    }
    for (auto [u, c] : G[v]) {
      if (dist[u + N * ticket] > d + c) {
        dist[u + N * ticket] = d + c;
        pq.push(al2{d + c, u + N * ticket});
      }
    }
  }
  ll ans = dist[N * (K + 1) - 1];
  cout << (ans == 1e18 ? -1ll : ans) << '\n';
}