#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <climits>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
// #include <atcoder/dsu>

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define all(a) a.begin(), a.end()
using namespace std;

template <class T> inline bool chmin(T &a, T b) {
	if (a > b) {
		a = b;
		return true;
	}
	return false;
}
template <class T> inline bool chmax(T &a, T b) {
	if (a < b) {
		a = b;
		return true;
	}
	return false;
}

template <class T1, class T2>
std::ostream &operator<<(std::ostream &out, const pair<T1, T2> &A) {
	cout << "{" << A.first << "," << A.second << "}";
	return out;
}

template <class T1, class T2>
std::ostream &operator<<(std::ostream &out, const map<T1, T2> &M) {
	for (const auto &A : M) {
		cout << "{" << A.first << "," << A.second << "}";
	}
	return out;
}

template <class T1>
std::ostream &operator<<(std::ostream &out, const set<T1> &M) {
	cout << "{";
	for (const auto &A : M) {
		cout << A << ", ";
	}
	cout << "}" << endl;
	return out;
}

template <class T1>
std::ostream &operator<<(std::ostream &out, const multiset<T1> &M) {
	cout << "{";
	for (const auto &A : M) {
		cout << A << ", ";
	}
	cout << "}" << endl;
	return out;
}

template <class T>
std::ostream &operator<<(std::ostream &out, const vector<T> &A) {
	for (const T &a : A) {
		cout << a << " ";
	}
	return out;
}

void print() { cout << endl; }

template <typename Head, typename... Tail> void print(Head H, Tail... T) {
	cout << H << " ";
	print(T...);
}

template <class T> std::istream &operator>>(std::istream &in, vector<T> &A) {
	for (T &a : A) {
		std::cin >> a;
	}
	return in;
}

using ll = long long;
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr ll LINF = numeric_limits<ll>::max() / 2;

struct Edge {
	int to;
	ll cost;
};

using Graph = vector<vector<Edge>>;
using Pll = pair<ll, ll>;

// ダイクストラ
void dijkstra(const Graph &G, int s, vector<ll> &dist) {
	int N = G.size();
	dist.assign(N, -1);
	dist[s] = 0;
	priority_queue<Pll, vector<Pll>, greater<Pll>> que;
	que.push({0, s});
	while (!que.empty()) {
		Pll p = que.top();
		que.pop();
		int v = p.second;
		if (dist[v] < p.first)
			continue;
		for (auto e : G[v]) {
			if (dist[e.to] == -1 || dist[e.to] > dist[v] + e.cost) {
				dist[e.to] = dist[v] + e.cost;
				que.push({dist[e.to], e.to});
			}
		}
	}
}

void solve() {
	// ここからスタート
	int N, M, K;
	cin >> N >> M >> K;
	vector<ll> C(M);
	rep(i, M) cin >> C[i];
	vector<pair<int, int>> E(M);
	rep(i, M) {
		int u, v;
		cin >> u >> v;
		u--;
		v--;
		E[i] = {u, v};
	}

	Graph G((K + 1) * N);
	rep(i, M) {
		auto [u, v] = E[i];
		ll c = C[i];
		rep(j, K + 1) {
			G[u + j * N].push_back({v + j * N, c});
			G[v + j * N].push_back({u + j * N, c});
			if (j < K) {
				G[u + j * N].push_back({v + (j + 1) * N, 0});
				G[v + j * N].push_back({u + (j + 1) * N, 0});
			}
		}
	}
	vector<ll> dist;
	dijkstra(G, 0, dist);
	vector<ll> ans;
	rep(i, K + 1) { ans.push_back(dist[K * N + N - 1]); }
	assert(int(ans.size()) == K + 1);
	if (count(all(ans), -1) == int(ans.size())) {
		cout << -1 << endl;
		return;
	}
	ll m = LINF;
	for (auto &a : ans) {
		if (a == -1)
			continue;
		chmin(m, a);
	}
	cout << m << endl;
}

int main(void) {
	std::cin.tie(0)->sync_with_stdio(0);
	solve();
	return 0;
}