#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m, k; cin >> n >> m >> k;
	vector<int>c(m);
	rep(i, m)cin >> c[i];
	vector to(n, vector<P>());
	rep(i, m) {
		int u, v; cin >> u >> v;
		u--, v--;
		to[u].emplace_back(v, c[i]);
		to[v].emplace_back(u, c[i]);
	}
	vector dp(n, vector<long long>(k + 1, LINF));
	dp[0][0] = 0;
	using T = std::pair<long long, P>;
	std::priority_queue<T, std::vector<T>, std::greater<T>> pq;
	pq.push({ dp[0][0], {0,0 } });
	while (!pq.empty()) {
		auto p = pq.top();
		pq.pop();
		long long cost = p.first;
		auto[pos, cnt] = p.second;
		if (dp[pos][cnt] < cost) continue;
		for (const auto &e : to[pos]) {
			if (cnt != k) {
				if (chmin(dp[e.first][cnt + 1], cost + 0)) {
					pq.push({ dp[e.first][cnt + 1], {e.first,cnt + 1 } });
				}
			}
			if (chmin(dp[e.first][cnt], cost + e.second)) {
				pq.push({ dp[e.first][cnt], {e.first,cnt } });
			}
		}
	}
	long long ans = LINF;
	rep(i, k + 1)chmin(ans, dp[n - 1][i]);
	if (ans == LINF)ans = -1;
	cout << ans << endl;
	return 0;
}