#include <iostream>
#include <vector>
#include <queue>

using namespace std;

#define MAX_V 100002
#define INF 1e15
typedef pair<int, int> pii;
typedef tuple<long long, int, int> tiii;

struct edge{
  int to, d;
};

int V,E,K;
long long weight[MAX_V][3];
vector<edge> G[MAX_V];

void dijkstra(int s) {
  priority_queue<tiii, vector<tiii>, greater<tiii>> Q;
  Q.push({0, s, K});
  weight[s][K] = 0;

  while (!Q.empty()) {
    auto [cost, v, coupons] = Q.top(); Q.pop();

    if (weight[v][coupons] < cost) continue;

    for (int i = 0; i < (int)G[v].size(); i++) {
      edge &e = G[v][i];

      if (coupons > 0 && weight[v][coupons] < weight[e.to][coupons-1]) {
        weight[e.to][coupons-1] = weight[v][coupons];
        Q.push({weight[e.to][coupons-1], e.to, coupons-1});
      }

      if ((long long)weight[v][coupons] + e.d < weight[e.to][coupons]) {
        weight[e.to][coupons] = weight[v][coupons] + e.d;
        Q.push({weight[e.to][coupons], e.to, coupons});
      }
    }
  }
}

void init() {
  for (int i = 0; i < MAX_V; i++) {
    G[i].clear();
    for (int j = 0; j < 3; j++) {
      weight[i][j] = INF;
    }
  }

  cin >> V >> E >> K;
  vector<int> toll(E);
  for (int i = 0; i < E; i++) {
    cin >> toll[i];
  }

  for (int i = 0; i < E; i++) {
    int u, v;
    cin >> u >> v;
    u--; v--;
    G[u].push_back({v, toll[i]});
    G[v].push_back({u, toll[i]});
  }
}

int main() {
  init();
  dijkstra(0);
  long long ans = INF;
  for (int i = 0; i < 3; i++) {
    ans = min(ans, weight[V-1][i]);
  }
  cout << (ans == INF ? -1 : ans) << endl;
}