/**
	author:  shobonvip
	created: 2025.04.19 23:03:50
**/

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

//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/

/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/

typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)
#define all(v) v.begin(), v.end()

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

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

template <typename T> T max(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
	return ret;
}

template <typename T> T min(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
	return ret;
}

template <typename T> T sum(vector<T> &a){
	T ret = 0;
	for (int i=0; i<(int)a.size(); i++) ret += a[i];
	return ret;
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	int n, m, k;
	cin >> n >> m >> k;
	vector<ll> c(m);
	rep(i,0,m) {
		cin >> c[i];
	}

	vector ikeru(n, vector<pair<int, ll>>(0));

	rep(i,0,m) {
		int u, v; cin >> u >> v;
		u--; v--;
		ikeru[u].push_back(pair(v, c[i]));
		ikeru[v].push_back(pair(u, c[i]));
	}

	vector d(k+1, vector<ll>(n, 1e18));
	d[k][0] = 0;
	priority_queue<tuple<ll,int,int>> pq;
	pq.push(make_tuple(0, k, 0));

	while(!pq.empty()){
		auto [tmp, nk, i] = pq.top();
		pq.pop();
		tmp = - tmp;
		if (tmp > d[nk][i]) continue;
		
		for (auto [j, w]: ikeru[i]) {
			ll cost = tmp + w;
			if (chmin(d[nk][j], cost)) {
				pq.push(make_tuple(- cost, nk, j));
			}
		}

		if (nk > 0) {
			for (auto [j, w]: ikeru[i]) {
				ll cost = tmp;
				if (chmin(d[nk-1][j], cost)) {
					pq.push(make_tuple(- cost, nk-1, j));
				}

			}
		}
	}

	ll ans = 1e18;
	rep(i,0,k+1) {
		chmin(ans, d[i][n-1]);
	}
	if (ans > 1e17) {
		cout << -1 << '\n';
	}else {
		cout << ans << '\n';
	}
}