#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

constexpr long long INF = 1002003004005006007;
vector<long long> dijkstra(const auto& to, int s = 0) {
  struct QueElem {
    int v;
    long long d;
    bool operator<(const QueElem& a) const { return d > a.d; }
    QueElem(int v, long long d) : v(v), d(d) {}
  };
  priority_queue<QueElem> q;
  vector<long long> dist(to.size(), INF);
  dist[s] = 0;
  q.emplace(s, 0);
  while (!q.empty()) {
    auto [u, d] = q.top(); q.pop();
    if (d > dist[u]) continue;
    for (auto [v, dv] : to[u]) {
      long long nd = d + dv;
      if (nd < dist[v]) {
        dist[v] = nd;
        q.emplace(v, nd);
      }
    }
  }
  return dist;
}


} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m, k;
  cin >> n >> m >> k;
  vector<vector<P>> to(4 * n);
  VI c(m);
  rep(i, m) cin >> c[i];
  rep(i, m) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    rep(_, 2) {
      rep(j, 4) {
        to[u + j * n].emplace_back(v + j * n, c[i]);
        if (j + 1 < 4) to[u + j * n].emplace_back(v + (j + 1) * n, 0);
      }
      swap(u, v);
    }
  }
  auto dist = dijkstra(to);
  ll ans = INF;
  rep(j, k + 1) chmin(ans, dist[n - 1 + j * n]);
  if (ans == INF) ans = -1;
  cout << ans << '\n';
}