#include<atcoder/all>
using namespace atcoder;

#include <bits/stdc++.h>
template<class T> inline bool chmin(T&a, T b){if(a > b){a = b; return true;}else{return false;}}
template<class T> inline bool chmax(T&a, T b){if(a < b){a = b; return true;}else{return false;}}
#define ll long long
#define double long double
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define mod (ll)(1e9+7)
#define inf (ll)(3e18+7)
#define eps (double)(1e-9)
#define pi (double) acos(-1)
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
using namespace std;

struct edge{
  ll to, cost;
};

vector<vector<edge>> G(400010);
vector<ll> d(400010, inf);

#define P pair<int, int>
void dijkstra(int s) {
	priority_queue<P, vector<P>, greater<P>>que;
	d[s] = 0;
	que.push(P(0, s));
	while (!que.empty()) {
		P p = que.top(); que.pop();
		int v = p.second;
		if (d[v] < p.first)continue;
		rep(i, G[v].size()) {
			edge e = G[v][i];
			if (d[e.to] > d[v] + e.cost) {
				d[e.to] = d[v] + e.cost;
				que.push(P(d[e.to], e.to));
			}
		}
	}
}

int main() {
    int n, m, K;
    cin >> n >> m >> K;
    vector<ll> c(m);
    rep(i, m)cin >> c[i];

    rep(i, m) {
        int u, v;
        cin >> u >> v;
        u--; v--;

        rep(k, K+1) {
            G[k * n + u].push_back({k * n + v, c[i]});
            G[k * n + v].push_back({k * n + u, c[i]});
        }

        rep(k, K) {
            G[(k+1) * n + u].push_back({k * n + v, 0});
            G[(k+1) * n + v].push_back({k * n + u, 0});
        }
    }

    dijkstra(K*n);
    ll ans = min({d[n-1], d[2*n-1], d[3*n-1]});
    cout << (ans == inf ? -1 : ans) << endl;
}