#include <bits/stdc++.h>
using namespace std;
template<class T> bool chmin(T& a, T b) { return a > b ? a = b, true : false; }
template<class T> bool chmax(T& a, T b) { return a < b ? a = b, true : false; }
template<typename T>
concept Iterable = requires(T t) { std::begin(t); std::end(t); };
template<typename T>
	requires Iterable<T> && (!is_same_v<T, string>)
ostream& operator<<(ostream& os, const T& container) { for (auto& element : container) os << element << ' '; return os; }
template<typename R>
	requires ranges::range<R> && (!is_same_v<decay_t<R>, string>) && (!is_same_v<decay_t<R>, const char*>)
ostream& operator<<(ostream& os, R&& range) { for (auto& element : range)os << element << ' '; return os; }
template<typename T>
	requires Iterable<T> && (!is_same_v<T, string>)
istream& operator>>(std::istream& is, T& container) { for (auto& e : container)is >> e; return is; }
using ll = long long;
using ull = unsigned long long;
using uint = unsigned int;
template<class T = ll> struct Edge {
	int to;
	T weight;
	bool operator==(Edge e) { return this->to == e.to and this->weight == e.weight; }
	bool operator<(Edge e) { return this->to == e.to ? this->weight < e.weight : this->to < e.to; }
};
#ifdef _DEBUG
#define SHOW(n) {const auto& _ret = n; cerr << #n << ": " << _ret << endl;}
#define MSG(x) cerr << x << endl;
#else
#define SHOW(n)
#define MSG(x)
#endif

//AtCoder Library
#include <atcoder/all>
using namespace atcoder;
//using mint = modint998244353;
using mint = modint1000000007;
//using mint1 = dynamic_modint<0>;
//using mint = modint;
//mint::set_mod();
istream& operator>>(istream& is, mint& x) { ll r; is >> r; x = r; return is; }
ostream& operator<<(ostream& os, mint& x) { os << x.val(); return os; }

//boost
//#include <boost/multiprecision/cpp_int.hpp>
//using namespace boost::multiprecision;
//using l3 = int128_t;



int main() {
	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int n, m, k;
	cin >> n >> m >> k;
	vector<ll> c(m);
	cin >> c;

	vector<vector<Edge<ll>>> g(n);
	for (int i = 0; i < m; ++i) {
		int a, b;
		cin >> a >> b;
		--a, --b;
		g[a].push_back({ b, c[i] });
		g[b].push_back({ a, c[i] });
	}

	const ll INF = 1e18;
	vector<vector<ll>> dp(k + 1, vector<ll>(n, INF));
	dp[0][0] = 0;
	using T = array<ll, 3>;
	priority_queue<T, vector<T>, greater<T>> que;
	que.push({ 0, 0, 0 });
	// dist, v, k
	
	while (not que.empty()) {
		auto [d, v, cnt] = que.top();
		que.pop();

		if (d > dp[cnt][v])continue;

		for (auto [s, w] : g[v]) {
			if (chmin(dp[cnt][s], dp[cnt][v] + w)) {
				que.push({ dp[cnt][s], s, cnt });
			}
			if (cnt + 1 <= k and chmin(dp[cnt + 1][s], dp[cnt][v])) {
				que.push({ dp[cnt + 1][s], s, cnt + 1 });
			}
			
		}
	}

	ll res = INF;
	for (int i = 0; i <= k; ++i) {
		chmin(res, dp[i][n - 1]);
	}

	if (res == INF)cout << -1 << endl;
	else cout << res << endl;



	return 0;
}